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Thapa G, Bhattacharya A, Bhattacharya S. Molecular dynamics investigation of DNA fragments bound to the anti-HIV protein SAMHD1 reveals alterations in allosteric communications. J Mol Graph Model 2024; 129:108748. [PMID: 38452417 DOI: 10.1016/j.jmgm.2024.108748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 02/16/2024] [Accepted: 02/20/2024] [Indexed: 03/09/2024]
Abstract
The sterile alpha motif and histidine-aspartate domain-containing protein 1 (or SAMHD1), a human dNTP-triphosphohydrolase, contributes to HIV-1 restriction in select terminally differentiated cells of the immune system. While the prevailing hypothesis is that the catalytically active form of the protein is an allosterically triggered tetramer, whose HIV-1 restriction properties are attributed to its dNTP - triphosphohydrolase activity, it is also known to bind to ssRNA and ssDNA oligomers. A complete picture of the structure-function relationship of the enzyme is still elusive and the function corresponding to its nucleic acid binding ability is debated. In this in silico study, we investigate the stability, preference and allosteric effects of DNA oligomers bound to SAMHD1. In particular, we compare the binding of DNA and RNA oligomers of the same sequence and also consider the binding of DNA fragments with phosphorothioate bonds in the backbone. The results are compared with the canonical form with the monomers connected by GTP/dATP crossbridges. The simulations indicate that SAMHD1 dimers preferably bind to DNA and RNA oligomers compared to GTP/dATP. However, allosteric communication channels are altered in the nucleic acid acid bound complexes compared to the canonical form. All results are consistent with the hypothesis that the DNA bound form of the protein correspond to an unproductive off-pathway state where the protein is sequestered and not available for dNTP hydrolysis.
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Affiliation(s)
- Gauri Thapa
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India.
| | | | - Swati Bhattacharya
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India.
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2
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Lv H, Cao Y, Zhu J, Liang Q. Molecular Insights into the Effect of Cholesterol on the Binding of Bicarbonate Ions in Band 3 Protein. Langmuir 2024. [PMID: 38739034 DOI: 10.1021/acs.langmuir.4c00216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
Band 3, or anion exchanger 1 (AE1), is one of the indispensable transmembrane proteins involved in the effective respiratory process of the human body and is primarily responsible for the exchange of bicarbonate and chloride anions across the plasma membrane of erythrocyte. However, the molecular mechanism of ion transport of Band 3 is not completely understood, yet. In this work, we systematically investigate the key binding sites of bicarbonate ions in Band 3 and the impact of cholesterol (CHOL) in lipid bilayers on bicarbonate ion binding using all-atom molecular dynamics (MD) simulations. We examine the dynamics of interactions of bicarbonate ions with Band 3 in the microsecond time scale and calculate the binding free energy of the anion in Band 3. The results indicate that the residue R730 of Band 3 is the most probable binding site for bicarbonate ions. CHOL enhances the bicarbonate ion binding by influencing the conformational stability of Band 3 and compressing the volume of the Band 3 cavity. These findings provide some insights into the bicarbonate ion binding in Band 3 and are helpful for understanding the anion exchange of Band 3.
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Affiliation(s)
- Haiying Lv
- Center for Statistical and Theoretical Condensed Matter Physics & Department of Physics, Zhejiang Normal University, Jinhua 321004, China
- Zhejiang Institute of Photoelectronics & Zhejiang Institute for Advanced Light Source, Zhejiang Normal University, Jinhua 321004, China
| | - Yu Cao
- Center for Statistical and Theoretical Condensed Matter Physics & Department of Physics, Zhejiang Normal University, Jinhua 321004, China
- Zhejiang Institute of Photoelectronics & Zhejiang Institute for Advanced Light Source, Zhejiang Normal University, Jinhua 321004, China
| | - Jin Zhu
- Center for Statistical and Theoretical Condensed Matter Physics & Department of Physics, Zhejiang Normal University, Jinhua 321004, China
- Zhejiang Institute of Photoelectronics & Zhejiang Institute for Advanced Light Source, Zhejiang Normal University, Jinhua 321004, China
| | - Qing Liang
- Center for Statistical and Theoretical Condensed Matter Physics & Department of Physics, Zhejiang Normal University, Jinhua 321004, China
- Zhejiang Institute of Photoelectronics & Zhejiang Institute for Advanced Light Source, Zhejiang Normal University, Jinhua 321004, China
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3
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Włodek F, Kulig W, Stachowicz-Kuśnierz A. Insights into short chain polyethylene penetration of phospholipid bilayers via atomistic molecular dynamics simulations. Biochim Biophys Acta Biomembr 2024; 1866:184327. [PMID: 38679310 DOI: 10.1016/j.bbamem.2024.184327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 04/16/2024] [Accepted: 04/23/2024] [Indexed: 05/01/2024]
Abstract
The escalation of global plastic production, reaching an annual output of 400 million tons, has significantly intensified concerns regarding plastic waste management. This has been exacerbated by improper recycling and disposal practices, contributing to the impending crisis of plastic pollution. Predictions indicate that by 2025, the environment will bear the burden of over ten billion metric tons of accumulated plastic waste. This situation has led to the concerning release of microplastics and nanoplastics (NPs) into the environment as plastic materials degrade, thereby posing risks to both ecosystems and human health. Nanoparticle interactions with living organisms have garnered significant attention due to their potential to disrupt vital biological processes. Of particular interest are lipid membranes, acting as crucial gatekeepers, underscoring the importance of comprehending the intricate process of NP penetration. Molecular dynamics (MD) simulations serve as a robust tool, offering molecular-level insights into these intricate interactions. In this study, we leverage all-atom MD simulations to delve into the interactions between lipid bilayers and polyethylene (PETH) chains of varying lengths. The investigation spans diverse lipid bilayer compositions-ranging from pure POPC to POPC:DPPC mixtures-revealing how PETH accommodates itself, adopts extended conformations, and influences membrane structure and ordering. Significantly, while longer PETH chains demonstrate limited passive diffusion, their potential to penetrate bilayers over extended timescales emerges as a significant revelation. Overall, this research significantly advances our comprehension of NP-membrane interactions, shedding light on the potential environmental and health implications that lie ahead.
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Affiliation(s)
- Franciszek Włodek
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland; Doctoral School of Exact and Natural Sciences, S. Łojasiewicza 11, 30-348 Krakow, Poland
| | - Waldemar Kulig
- Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
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4
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Kasparyan G, Hub JS. Molecular Simulations Reveal the Free Energy Landscape and Transition State of Membrane Electroporation. Phys Rev Lett 2024; 132:148401. [PMID: 38640376 DOI: 10.1103/physrevlett.132.148401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Accepted: 02/29/2024] [Indexed: 04/21/2024]
Abstract
The formation of pores over lipid membranes by the application of electric fields, termed membrane electroporation, is widely used in biotechnology and medicine to deliver drugs, vaccines, or genes into living cells. Continuum models for describing the free energy landscape of membrane electroporation were proposed decades ago, but they have never been tested against spatially detailed atomistic models. Using molecular dynamics (MD) simulations with a recently proposed reaction coordinate, we computed potentials of mean force of pore nucleation and pore expansion in lipid membranes at various transmembrane potentials. Whereas the free energies of pore expansion are compatible with previous continuum models, the experimentally important free energy barrier of pore nucleation is at variance with established models. The discrepancy originates from different geometries of the transition state; previous continuum models assumed the presence of a membrane-spanning defect throughout the process, whereas, according to the MD simulations, the transition state of pore nucleation is typically passed before a transmembrane defect has formed. A modified continuum model is presented that qualitatively agrees with the MD simulations. Using kinetics of pore opening together with transition state theory, our free energies of pore nucleation are in excellent agreement with previous experimental data.
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Affiliation(s)
- Gari Kasparyan
- Theoretical Physics and Center for Biophysics, Saarland University, 66123 Saarbrücken, Germany
| | - Jochen S Hub
- Theoretical Physics and Center for Biophysics, Saarland University, 66123 Saarbrücken, Germany
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5
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Hassanpour M, Torabi SM, Afshar D, Kowsari MH, Meratan AA, Nikfarjam N. Tracing the Antibacterial Performance of Bis-Imidazolium-based Ionic Liquid Derivatives. ACS Appl Bio Mater 2024; 7:1558-1568. [PMID: 38373341 DOI: 10.1021/acsabm.3c01040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
Ionic liquid (IL) cationic species have recently captivated the attention of pharmacists, biochemists, and biomedical scientists as promising antibacterial agents to deal with the multidrug resistance bacteria crisis. The structure and functional groups of ILs influence their physiochemical properties and biological activities. However, a comprehensive study is required to fully understand the details of the antibacterial activity of ILs carrying various functional groups. Herein, dicationic ILs (DCILs) are reported based on imidazolium rings as efficient antibacterial agents. The DCILs carried various functionalities such as 2-hydroxybutyl (DCIL-1), 2-hydroxy-3-isopropoxypropyl (DCIL-2), 2-hydroxy-3-(methacryloyloxy)propyl (DCIL-3), 2-hydroxy-2-phenylethyl (DCIL-4), and 2-hydroxy-3-phenoxypropyl (DCIL-5). The structure-antibacterial activity relationships of the DCILs against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were comprehensively studied through antibacterial tests, morphology analysis, and adhesion tests. The experimental assays revealed an antibacterial efficacy order of DCIL-5 > DCIL-1 > DCIL-4 > DCIL-2 > DCIL-3. The all-atom molecular dynamics (MD) simulation showed a deep permeation of the hydrophobic -OPh functional group of DCIL-5 through the E. coli membrane model in agreement with the experimental observations. Current findings assist scientists in designing new task-specific DCILs for effective interactions with biological membranes for different applications.
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Affiliation(s)
- Mahnaz Hassanpour
- Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
| | - Seyed Mohammad Torabi
- Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
| | - Davoud Afshar
- Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan 45139-56111, Iran
| | - Mohammad Hossein Kowsari
- Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
- Center for Research in Climate Change and Global Warming (CRCC), Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
| | - Ali Akbar Meratan
- Department of Biological Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
| | - Nasser Nikfarjam
- Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
- Department of Chemical Engineering, College of Engineering and Computing, University of South Carolina, Columbia, South Carolina 29208, United States
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6
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Jarin Z, Venable RM, Han K, Pastor RW. Ion-Induced PIP2 Clustering with Martini3: Modification of Phosphate-Ion Interactions and Comparison with CHARMM36. J Phys Chem B 2024; 128:2134-2143. [PMID: 38393820 DOI: 10.1021/acs.jpcb.3c06523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP2) is a critical lipid for cellular signaling. The specific phosphorylation of the inositol ring controls protein binding as well as clustering behavior. Two popular models to describe ion-mediated clustering of PIP2 are Martini3 (M3) and CHARMM36 (C36). Molecular dynamics simulations of PIP2-containing bilayers in solutions of potassium chloride, sodium chloride, and calcium chloride, and at two different resolutions are performed to understand the aggregation and the model parameters that drive it. The average M3 clusters of PIP2 in bilayers of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine and PIP2 bilayers in the presence of K+, Na+, or Ca2+ contained 2.2, 2.6, and 6.4 times more PIP2 than C36 clusters, respectively. Indeed, the Ca2+-containing systems often formed a single large aggregate. Reparametrization of the M3 ion-phosphate Lennard-Jones interaction energies to reproduce experimental osmotic pressure of sodium dimethyl phosphate (DMP), K[DMP], and Ca[DMP]2 solutions, the same experimental target as C36, yielded comparably sized PIP2 clusters for the two models. Furthermore, C36 and the modified M3 predict similar saturation of the phosphate groups with increasing Ca2+, although the coarse-grained model does not capture the cooperativity between K+ and Ca2+. This characterization of the M3 behavior in the presence of monovalent and divalent ions lays a foundation to study cation/protein/PIP2 clustering.
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Affiliation(s)
- Zack Jarin
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, Maryland 20892, United States
| | - Richard M Venable
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, Maryland 20892, United States
| | - Kyungreem Han
- Laboratory of Computational Neurophysics, Center for Brain Technology, Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Korea
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, Maryland 20892, United States
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7
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Vaiwala R, Ayappa KG. Martini-3 Coarse-Grained Models for the Bacterial Lipopolysaccharide Outer Membrane of Escherichia coli. J Chem Theory Comput 2024; 20:1704-1716. [PMID: 37676287 DOI: 10.1021/acs.jctc.3c00471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
The outer lipopolysaccharide (LPS) membrane of Gram-negative bacteria forms the main barrier for transport of antimicrobial molecules into the bacterial cell. In this study we develop coarse-grained models for the outer membrane of Escherichia coli in the Martini-3 framework. The coarse-grained model force field was parametrized and validated using all-atom simulations of symmetric membranes of lipid A and rough LPS as well as a complete asymmetric membrane of LPS with the O-antigen. The bonded parameters were obtained using an iterative refinement procedure with target bonded distributions obtained from all-atom simulations. The membrane thickness, area of the LPS, and density distributions for the different regions as well as the water and ion densities in Martini-3 simulations show excellent agreement with the all-atom data. Additionally the solvent accessible surface area for individual molecules in water was found to be in good agreement. The binding of calcium ions with phosphate and carboxylate moieties of LPS is accurately captured in the Martini-3 model, indicative of the integrity of the highly negatively charged LPS molecules in the outer membranes of Gram-negative bacteria. The melting transition of the coarse-grained lipid A membrane model was found to occur between 300 and 310 K, and the model captured variations in area per LPS, order parameter, and membrane thickness across the melting transition. Our study reveals that the proposed Martini-3 models for LPS are able to capture the physicochemical balance of the complex sugar architecture of the outer membrane of Escherichia coli. The coarse-grained models developed in this study would be useful for determining membrane protein interactions and permeation of potential antimicrobials through bacterial membranes at mesoscopic spatial and temporal scales.
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Affiliation(s)
- Rakesh Vaiwala
- Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India
| | - K Ganapathy Ayappa
- Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India
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8
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Bouquiaux C, Champagne B, Beaujean P. Multimillion Atom Simulations of Di-8-ANEPPS Chromophores Embedded in a Model Plasma Membrane: Toward the Investigation of Realistic Dyed Cell Membranes. J Chem Inf Model 2024; 64:518-531. [PMID: 38157204 DOI: 10.1021/acs.jcim.3c01568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
A multistep computational approach has been employed to study a multimillion all-atom dyed plasma membrane, with no less than 42 different lipid species spanning the major head groups and a variety of fatty acids, as well as cholesterol, with the objective of investigating its structure and dynamics, as well as its impact on the embedded di-8-ANEPPS dyes. The latter are commonly used as bioimaging probes and serve as local microscopes. So, they provide information on membrane morphology via their second harmonic nonlinear optical (NLO) responses, which have the advantage of being specific to interface regions and sensitive to the chromophore environment. In previous studies, this chromophore has only been studied in simpler membrane models, far from the complexity of real lipid bilayers, while, owing to the ever-increasing computational resources, multimillion lipid bilayers have been studied, giving access to the effects of its heterogeneity. First, using molecular dynamics (MD) simulations, it is found that the combination of lipids produces a more ordered and denser membrane compared to its homogeneous model counterparts, while the local environment of the embedded dyes becomes enriched in phosphatidylcholine. Subsequently, the second harmonic first hyperpolarizability of the probes was calculated at the TDDFT level on selected frames of MD, highlighting the influence of the lipid environment. Due to the complexity of the system, machine learning (ML) tools have been employed to establish relationships between the membrane structural parameters, the orientation of the probes, and their NLO responses. These ML approaches have revealed influential features, including the presence of diacylglycerol lipids close to the dye. On the whole, this work provides a first step toward understanding the cooperation, synergy, and interactions that occur in such complex guest-host environments, which have emerged as new targets for drug design and membrane lipid therapy.
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Affiliation(s)
- Charlotte Bouquiaux
- University of Namur, Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, rue de Bruxelles, 61, B-5000 Namur, Belgium
| | - Benoît Champagne
- University of Namur, Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, rue de Bruxelles, 61, B-5000 Namur, Belgium
| | - Pierre Beaujean
- University of Namur, Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, rue de Bruxelles, 61, B-5000 Namur, Belgium
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9
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Delgado JM, Nagy PR, Varma S. Polarizable AMOEBA Model for Simulating Mg 2+·Protein·Nucleotide Complexes. J Chem Inf Model 2024; 64:378-392. [PMID: 38051630 DOI: 10.1021/acs.jcim.3c01513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Molecular mechanics (MM) simulations have the potential to provide detailed insights into the mechanisms of enzymes that utilize nucleotides as cofactors. In most cases, the activities of these enzymes also require the binding of divalent cations to catalytic sites. However, modeling divalent cations in MM simulations has been challenging. The inclusion of explicit polarization was considered promising, but despite improvements over nonpolarizable force fields and despite the inclusion of "Nonbonded-fix (NB-fix)" corrections, errors in interaction energies of divalent cations with proteins remain large. Importantly, the application of these models fails to reproduce the experimental structural data on Mg2+·Protein·ATP complexes. Focusing on these complexes, here we provide a systematic assessment of the polarizable AMOEBA model and recommend critical changes that substantially improve its predictive performance. Our key results are as follows. We first show that our recent revision of the AMOEBA protein model (AMOEBABIO18-HFC), which contains high field corrections (HFCs) to induced dipoles, dramatically improves Mg2+-protein interaction energies, reducing the mean absolute error (MAE) from 17 to 10 kcal/mol. This further supports the general applicability of AMOEBABIO18-HFC. The inclusion of many-body NB-fix corrections further reduces MAE to 6 kcal/mol, which amounts to less than 2% error. The errors are estimated with respect to vdW-inclusive density functional theory that we benchmark against CCSD(T) calculations and experiments. We also present a new model of ATP with revised polarization parameters to better capture its high field response, as well as new vdW and dihedral parameters. The ATP model accurately predicts experimental Mg2+-ATP binding free energy in the aqueous phase and provides new insights into how Mg2+ associates with ATP. Finally, we show that molecular dynamics (MD) simulations of Mg2+·Kinase·ATP complexes carried out with these improvements lead to a better agreement in global and local catalytic site structures between MD and X-ray crystallography.
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Affiliation(s)
- Julian M Delgado
- Department of Molecular Biosciences, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States
| | - Péter R Nagy
- Department of Physical Chemistry and Materials Science, Faculty of Chemical Technology and Biotechnology, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest H-1111, Hungary
- HUN-REN-BME Quantum Chemistry Research Group, Műegyetem rkp. 3., Budapest H-1111, Hungary
- MTA-BME Lendület Quantum Chemistry Research Group, Műegyetem rkp. 3., Budapest H-1111, Hungary
| | - Sameer Varma
- Department of Molecular Biosciences, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States
- Department of Physics, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States
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10
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Blazhynska M, Gumbart JC, Chen H, Tajkhorshid E, Roux B, Chipot C. A Rigorous Framework for Calculating Protein-Protein Binding Affinities in Membranes. J Chem Theory Comput 2023; 19:9077-9092. [PMID: 38091976 DOI: 10.1021/acs.jctc.3c00941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Calculating the binding free energy of integral transmembrane (TM) proteins is crucial for understanding the mechanisms by which they recognize one another and reversibly associate. The glycophorin A (GpA) homodimer, composed of two α-helical segments, has long served as a model system for studying TM protein reversible association. The present work establishes a methodological framework for calculating the binding affinity of the GpA homodimer in the heterogeneous environment of a membrane. Our investigation carefully considered a variety of protocols, including the appropriate choice of the force field, rigorous standardization reflecting the experimental conditions, sampling algorithm, anisotropic environment, and collective variables, to accurately describe GpA dimerization via molecular dynamics-based approaches. Specifically, two strategies were explored: (i) an unrestrained potential mean force (PMF) calculation, which merely enhances sampling along the separation of the two binding partners without any restraint, and (ii) a so-called "geometrical route", whereby the α-helices are progressively separated with imposed restraints on their orientational, positional, and conformational degrees of freedom to accelerate convergence. Our simulations reveal that the simplified, unrestrained PMF approach is inadequate for the description of GpA dimerization. Instead, the geometrical route, tailored specifically to GpA in a membrane environment, yields excellent agreement with experimental data within a reasonable computational time. A dimerization free energy of -10.7 kcal/mol is obtained, in fairly good agreement with available experimental data. The geometrical route further helps elucidate how environmental forces drive association before helical interactions stabilize it. Our simulations also brought to light a distinct, long-lived spatial arrangement that potentially serves as an intermediate state during dimer formation. The methodological advances in the generalized geometrical route provide a powerful tool for accurate and efficient binding-affinity calculations of intricate TM protein complexes in inhomogeneous environments.
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Affiliation(s)
- Marharyta Blazhynska
- Laboratoire International Associé Centre National de la Recherche Scientifique et University of Illinois at Urbana-Champaign, Unité Mixte de Recherche n°7019, Université de Lorraine, B.P. 70239, Vandœuvre-lès-Nancy cedex 54506, France
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332, United States
| | - Haochuan Chen
- Laboratoire International Associé Centre National de la Recherche Scientifique et University of Illinois at Urbana-Champaign, Unité Mixte de Recherche n°7019, Université de Lorraine, B.P. 70239, Vandœuvre-lès-Nancy cedex 54506, France
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Avenue, Urbana, Illinois 61801, United States
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, United States
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th Street W225, Chicago, Illinois 60637, United States
- Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, Illinois 60637, United States
| | - Christophe Chipot
- Laboratoire International Associé Centre National de la Recherche Scientifique et University of Illinois at Urbana-Champaign, Unité Mixte de Recherche n°7019, Université de Lorraine, B.P. 70239, Vandœuvre-lès-Nancy cedex 54506, France
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Avenue, Urbana, Illinois 61801, United States
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th Street W225, Chicago, Illinois 60637, United States
- Department of Chemistry, The University of Hawai'i at Ma̅noa, 2545 McCarthy Mall, Honolulu, Hawaii 96822, United States
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11
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Xu J, Karra V, Large DE, Auguste DT, Hung FR. Understanding the Mechanical Properties of Ultradeformable Liposomes Using Molecular Dynamics Simulations. J Phys Chem B 2023; 127:9496-9512. [PMID: 37879075 PMCID: PMC10641833 DOI: 10.1021/acs.jpcb.3c04386] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 09/19/2023] [Accepted: 10/04/2023] [Indexed: 10/27/2023]
Abstract
Improving drug delivery efficiency to solid tumor sites is a central challenge in anticancer therapeutic research. Our previous experimental study (Guo et al., Nat. Commun. 2018, 9, 130) showed that soft, elastic liposomes had increased uptake and accumulation in cancer cells and tumors in vitro and in vivo respectively, relative to rigid particles. As a first step toward understanding how liposomes' molecular structure and composition modulates their elasticity, we performed all-atom and coarse-grained classical molecular dynamics (MD) simulations of lipid bilayers formed by mixing a long-tailed unsaturated phospholipid with a short-tailed saturated lipid with the same headgroup. The former types of phospholipids considered were 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine (termed here DPMPC). The shorter saturated lipids examined were 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), 1,2-didecanoyl-sn-glycero-3-phosphocholine (DDPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Several lipid concentrations and surface tensions were considered. Our results show that DOPC or DPMPC systems having 25-35 mol % of the shortest lipids DHPC or DDPC are the least rigid, having area compressibility moduli KA that are ∼10% smaller than the values observed in pure DOPC or DPMPC bilayers. These results agree with experimental measurements of the stretching modulus and lysis tension in liposomes with the same compositions. These mixed systems also have lower areas per lipid and form more uneven x-y interfaces with water, the tails of both primary and secondary lipids are more disordered, and the terminal methyl groups in the tails of the long lipid DOPC or DPMPC wriggle more in the vertical direction, compared to pure DOPC or DPMPC bilayers or their mixtures with the longer saturated lipid DLPC or DMPC. These observations confirm our hypothesis that adding increasing concentrations of the short unsaturated lipid DHPC or DDPC to DOPC or DPMPC bilayers alters lipid packing and thus makes the resulting liposomes more elastic and less rigid. No formation of lipid nanodomains was noted in our simulations, and no clear trends were observed in the lateral diffusivities of the lipids as the concentration, type of secondary lipid, and surface tension were varied.
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Affiliation(s)
- Jiaming Xu
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Vyshnavi Karra
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Danielle E. Large
- Department
of Bioengineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Debra T. Auguste
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
- Department
of Bioengineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Francisco R. Hung
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
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12
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Karal MAS, Billah MM, Ahmed M, Ahamed MK. A review on the measurement of the bending rigidity of lipid membranes. Soft Matter 2023; 19:8285-8304. [PMID: 37873600 DOI: 10.1039/d3sm00882g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
This review provides an overview of the latest developments in both experimental and simulation techniques used to assess the bending rigidity of lipid membranes. It places special emphasis on experimental methods that utilize model vesicles to manipulate lipid compositions and other experimental parameters to determine the bending rigidity of the membrane. It also describes two commonly used simulation methods for estimating bending rigidity. The impact of various factors on membrane bending rigidity is summarized, including cholesterol, lipids, salt concentration, surface charge, membrane phase state, peptides, proteins, and polyethylene glycol. These factors are shown to influence the bending rigidity, contributing to a better understanding of the biophysical properties of membranes and their role in biological processes. Furthermore, the review discusses future directions and potential advancements in this research field, highlighting areas where further investigation is required.
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Affiliation(s)
- Mohammad Abu Sayem Karal
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh.
| | - Md Masum Billah
- Department of Physics, Jashore University of Science and Technology, Jashore 7408, Bangladesh
| | - Marzuk Ahmed
- Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka 422-8529, Japan
| | - Md Kabir Ahamed
- Radiation, Transport and Waste Safety Division, Bangladesh Atomic Energy Regulatory Authority, Agargaon, Dhaka 1207, Bangladesh
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13
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Abdelmessih R, Xu J, Hung FR, Auguste DT. Integration of an LPAR1 Antagonist into Liposomes Enhances Their Internalization and Tumor Accumulation in an Animal Model of Human Metastatic Breast Cancer. Mol Pharm 2023; 20:5500-5514. [PMID: 37844135 PMCID: PMC10631474 DOI: 10.1021/acs.molpharmaceut.3c00348] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 09/29/2023] [Accepted: 10/02/2023] [Indexed: 10/18/2023]
Abstract
Lysophosphatidic acid receptor 1 (LPAR1) is elevated in breast cancer. The deregulation of LPAR1, including the function and level of expression, is linked to cancer initiation, progression, and metastasis. LPAR1 antagonists, AM095 or Ki16425, may be effective therapeutic molecules, yet their limited water solubility hinders in vivo delivery. In this study, we report on the synthesis of two liposomal formulations incorporating AM095 or Ki16425, embedded within the lipid bilayer, as targeted nanocarriers for metastatic breast cancer (MBC). The data show that the Ki16425 liposomal formulation exhibited a 50% increase in internalization by MBC mouse epithelial cells (4T1) and a 100% increase in tumor accumulation in a mouse model of MBC compared with that of a blank liposomal formulation (control). At the same time, normal mouse epithelial cells (EpH-4Ev) internalized the Ki16425 liposomal formulation 25% lesser than the control formulation. Molecular dynamics simulations show that the integration of AM095 or Ki16425 modified the physical and mechanical properties of the lipid bilayer, making it more flexible in these liposomal formulations compared with liposomes without drug. The incorporation of an LPAR1 antagonist within a liposomal drug delivery system represents a viable therapeutic approach for targeting the LPA-LPAR1 axis, which may hinder the progression of MBC.
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Affiliation(s)
- Rudolf
G. Abdelmessih
- Department of Chemical Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Jiaming Xu
- Department of Chemical Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Francisco R. Hung
- Department of Chemical Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Debra T. Auguste
- Department of Chemical Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
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14
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Khalid S, Brandner AF, Juraschko N, Newman KE, Pedebos C, Prakaash D, Smith IPS, Waller C, Weerakoon D. Computational microbiology of bacteria: Advancements in molecular dynamics simulations. Structure 2023; 31:1320-1327. [PMID: 37875115 DOI: 10.1016/j.str.2023.09.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 09/04/2023] [Accepted: 09/28/2023] [Indexed: 10/26/2023]
Abstract
Microbiology is traditionally considered within the context of wet laboratory methodologies. Computational techniques have a great potential to contribute to microbiology. Here, we describe our loose definition of "computational microbiology" and provide a short survey focused on molecular dynamics simulations of bacterial systems that fall within this definition. It is our contention that increased compositional complexity and realistic levels of molecular crowding within simulated systems are key for bridging the divide between experimental and computational microbiology.
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Affiliation(s)
- Syma Khalid
- Department of Biochemistry, University of Oxford, OX1 3QU Oxford, UK; School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK.
| | - Astrid F Brandner
- Department of Biochemistry, University of Oxford, OX1 3QU Oxford, UK
| | - Nikolai Juraschko
- Department of Biochemistry, University of Oxford, OX1 3QU Oxford, UK; Artificial Intelligence and Informatics, The Rosalind Franklin Institute, Didcot, UK
| | - Kahlan E Newman
- School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK
| | - Conrado Pedebos
- Department of Biochemistry, University of Oxford, OX1 3QU Oxford, UK; Programa de Pós-Graduação em Biociências (PPGBio), Universidade Federal de Ciências da Saúde de Porto Alegre - UFCSPA, Porto Alegre, Brazil
| | - Dheeraj Prakaash
- Department of Biochemistry, University of Oxford, OX1 3QU Oxford, UK
| | - Iain P S Smith
- School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK
| | - Callum Waller
- School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK
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15
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Hempelmann P, Lolicato F, Graziadei A, Brown RDR, Spiegel S, Rappsilber J, Nickel W, Höglinger D, Jamecna D. The sterol transporter STARD3 transports sphingosine at ER-lysosome contact sites. bioRxiv 2023:2023.09.18.557036. [PMID: 37790546 PMCID: PMC10542139 DOI: 10.1101/2023.09.18.557036] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Sphingolipids are important structural components of membranes. Additionally, simple sphingolipids such as sphingosine are highly bioactive and participate in complex subcellular signaling. Sphingolipid deregulation is associated with many severe diseases including diabetes, Parkinson's and cancer. Here, we focus on how sphingosine, generated from sphingolipid catabolism in late endosomes/lysosomes, is reintegrated into the biosynthetic machinery at the endoplasmic reticulum (ER). We characterized the sterol transporter STARD3 as a sphingosine transporter acting at lysosome-ER contact sites. Experiments featuring crosslinkable sphingosine probes, supported by unbiased molecular dynamics simulations, exposed how sphingosine binds to the lipid-binding domain of STARD3. Following the metabolic fate of pre-localized lysosomal sphingosine showed the importance of STARD3 and its actions at contact sites for the integration of sphingosine into ceramide in a cellular context. Our findings provide the first example of interorganellar sphingosine transfer and pave the way for a better understanding of sphingolipid - sterol co-regulation.
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Affiliation(s)
- Pia Hempelmann
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg
| | - Fabio Lolicato
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg
- Department of Physics, University of Helsinki, FI-00014 Helsinki, Finland
| | - Andrea Graziadei
- Institute for Biotechnology, Technical University Berlin, Gustav Mayer Allee 25, 13355 Berlin
| | - Ryan D R Brown
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA
| | - Sarah Spiegel
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA
| | - Juri Rappsilber
- Institute for Biotechnology, Technical University Berlin, Gustav Mayer Allee 25, 13355 Berlin
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg
| | - Doris Höglinger
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg
| | - Denisa Jamecna
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg
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16
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Back D, O’Donnell TJ, Axt KK, Gurr JR, Vanegas JM, Williams PG, Philmus B. Identification, Heterologous Expression, and Characterization of the Tolypodiol Biosynthetic Gene Cluster through an Integrated Approach. ACS Chem Biol 2023; 18:1797-1807. [PMID: 37487226 PMCID: PMC10529828 DOI: 10.1021/acschembio.3c00225] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
Cyanobacteria are tremendous producers of biologically active natural products, including the potent anti-inflammatory compound tolypodiol. However, linking biosynthetic gene clusters with compound production in cyanobacteria has lagged behind that in other bacterial genera. Tolypodiol is a meroterpenoid originally isolated from the cyanobacterium HT-58-2. Here we describe the identification of the tolypodiol biosynthetic gene cluster through heterologous expression in Anabaena and in vitro protein assays of a methyltransferase found in the tolypodiol biosynthetic gene cluster. We have also identified similar biosynthetic gene clusters in cyanobacterial and actinobacterial genomes, suggesting that meroterpenoids with structural similarity to the tolypodiols may be synthesized by other microbes. We also report the identification of two new analogs of tolypodiol that we have identified in both the original and heterologous producer. This work further illustrates the usefulness of Anabaena as a heterologous expression host for cyanobacterial compounds and how integrated approaches can help to link natural product compounds with their producing biosynthetic gene clusters.
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Affiliation(s)
- Daniel Back
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, OR 97331, U.S.A
| | - Timothy J. O’Donnell
- Department of Chemistry, University of Hawai’i at Mānoa, Honolulu, HI 96822, U.S.A
| | - Kyle K. Axt
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, OR 97331, U.S.A
| | - Joshua R. Gurr
- Department of Chemistry, University of Hawai’i at Mānoa, Honolulu, HI 96822, U.S.A
| | - Juan M. Vanegas
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, U.S.A
| | - Philip G. Williams
- Department of Chemistry, University of Hawai’i at Mānoa, Honolulu, HI 96822, U.S.A
| | - Benjamin Philmus
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, OR 97331, U.S.A
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17
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Poudel B, Rajeshwar T R, Vanegas JM. Membrane mediated mechanical stimuli produces distinct active-like states in the AT1 receptor. Nat Commun 2023; 14:4690. [PMID: 37542033 PMCID: PMC10403497 DOI: 10.1038/s41467-023-40433-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 07/27/2023] [Indexed: 08/06/2023] Open
Abstract
The Angiotensin II Type 1 (AT1) receptor is one of the most widely studied GPCRs within the context of biased signaling. While the AT1 receptor is activated by agonists such as the peptide AngII, it can also be activated by mechanical stimuli such as membrane stretch or shear in the absence of a ligand. Despite the importance of mechanical activation of the AT1 receptor in biological processes such as vasoconstriction, little is known about the structural changes induced by external physical stimuli mediated by the surrounding lipid membrane. Here, we present a systematic simulation study that characterizes the activation of the AT1 receptor under various membrane environments and mechanical stimuli. We show that stability of the active state is highly sensitive to membrane thickness and tension. Structural comparison of membrane-mediated vs. agonist-induced activation shows that the AT1 receptor has distinct active conformations. This is supported by multi-microsecond free energy calculations that show unique landscapes for the inactive and various active states. Our modeling results provide structural insights into the mechanical activation of the AT1 receptor and how it may produce different functional outcomes within the framework of biased agonism.
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Affiliation(s)
- Bharat Poudel
- Materials Science Graduate Program, The University of Vermont, Burlington, VT, 05405, USA
| | - Rajitha Rajeshwar T
- Department of Physics, The University of Vermont, Burlington, VT, 05405, USA
| | - Juan M Vanegas
- Materials Science Graduate Program, The University of Vermont, Burlington, VT, 05405, USA.
- Department of Physics, The University of Vermont, Burlington, VT, 05405, USA.
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97330, USA.
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18
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Schäffler M, Samantray S, Strodel B. Transition Networks Unveil Disorder-to-Order Transformations in A β Caused by Glycosaminoglycans or Lipids. Int J Mol Sci 2023; 24:11238. [PMID: 37510997 PMCID: PMC10380057 DOI: 10.3390/ijms241411238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 07/02/2023] [Accepted: 07/04/2023] [Indexed: 07/30/2023] Open
Abstract
The aggregation of amyloid-β (Aβ) peptides, particularly of Aβ1-42, has been linked to the pathogenesis of Alzheimer's disease. In this study, we focus on the conformational change of Aβ1-42 in the presence of glycosaminoglycans (GAGs) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipids using molecular dynamics simulations. We analyze the conformational changes that occur in Aβ by extracting the key structural features that are then used to generate transition networks. Using the same three features per network highlights the transitions from intrinsically disordered states ubiquitous in Aβ1-42 in solution to more compact states arising from stable β-hairpin formation when Aβ1-42 is in the vicinity of a GAG molecule, and even more compact states characterized by a α-helix or β-sheet structures when Aβ1-42 interacts with a POPC lipid cluster. We show that the molecular mechanisms underlying these transitions from disorder to order are different for the Aβ1-42/GAG and Aβ1-42/POPC systems. While in the latter the hydrophobicity provided by the lipid tails facilitates the folding of Aβ1-42, in the case of GAG there are hardly any intermolecular Aβ1-42-GAG interactions. Instead, GAG removes sodium ions from the peptide, allowing stronger electrostatic interactions within the peptide that stabilize a β-hairpin. Our results contribute to the growing knowledge of the role of GAGs and lipids in the conformational preferences of the Aβ peptide, which in turn influences its aggregation into toxic oligomers and amyloid fibrils.
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Affiliation(s)
- Moritz Schäffler
- Institute of Biological Information Processing, Structural Biochemistry (IBI-7), Forschungszentrum Jülich, 52428 Jülich, Germany
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Suman Samantray
- Institute of Biological Information Processing, Structural Biochemistry (IBI-7), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Birgit Strodel
- Institute of Biological Information Processing, Structural Biochemistry (IBI-7), Forschungszentrum Jülich, 52428 Jülich, Germany
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
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19
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Winter SL, Golani G, Lolicato F, Vallbracht M, Thiyagarajah K, Ahmed SS, Lüchtenborg C, Fackler OT, Brügger B, Hoenen T, Nickel W, Schwarz US, Chlanda P. The Ebola virus VP40 matrix layer undergoes endosomal disassembly essential for membrane fusion. EMBO J 2023:e113578. [PMID: 37082863 DOI: 10.15252/embj.2023113578] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 03/09/2023] [Accepted: 03/22/2023] [Indexed: 04/22/2023] Open
Abstract
Ebola viruses (EBOVs) assemble into filamentous virions, whose shape and stability are determined by the matrix viral protein 40 (VP40). Virus entry into host cells occurs via membrane fusion in late endosomes; however, the mechanism of how the remarkably long virions undergo uncoating, including virion disassembly and nucleocapsid release into the cytosol, remains unknown. Here, we investigate the structural architecture of EBOVs entering host cells and discover that the VP40 matrix disassembles prior to membrane fusion. We reveal that VP40 disassembly is caused by the weakening of VP40-lipid interactions driven by low endosomal pH that equilibrates passively across the viral envelope without a dedicated ion channel. We further show that viral membrane fusion depends on VP40 matrix integrity, and its disassembly reduces the energy barrier for fusion stalk formation. Thus, pH-driven structural remodeling of the VP40 matrix acts as a molecular switch coupling viral matrix uncoating to membrane fusion during EBOV entry.
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Affiliation(s)
- Sophie L Winter
- Schaller Research Groups, Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
- BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - Gonen Golani
- BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany
| | - Fabio Lolicato
- Heidelberg University Biochemistry Center, Heidelberg, Germany
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Melina Vallbracht
- Schaller Research Groups, Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
- BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - Keerthihan Thiyagarajah
- Schaller Research Groups, Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
- BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - Samy Sid Ahmed
- Department of Infectious Diseases, Integrative Virology, University Hospital Heidelberg, Heidelberg, Germany
| | | | - Oliver T Fackler
- Department of Infectious Diseases, Integrative Virology, University Hospital Heidelberg, Heidelberg, Germany
- German Centre for Infection Research (DZIF), Partner Site Heidelberg, Heidelberg, Germany
| | - Britta Brügger
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Thomas Hoenen
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Insitut, Greifswald-Insel Riems, Greifswald, Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Ulrich S Schwarz
- BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
- Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany
| | - Petr Chlanda
- Schaller Research Groups, Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
- BioQuant-Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
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20
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Papadopoulos N, Nédélec A, Derenne A, Şulea TA, Pecquet C, Chachoua I, Vertenoeil G, Tilmant T, Petrescu AJ, Mazzucchelli G, Iorga BI, Vertommen D, Constantinescu SN. Oncogenic CALR mutant C-terminus mediates dual binding to the thrombopoietin receptor triggering complex dimerization and activation. Nat Commun 2023; 14:1881. [PMID: 37019903 PMCID: PMC10076285 DOI: 10.1038/s41467-023-37277-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 03/04/2023] [Indexed: 04/07/2023] Open
Abstract
Calreticulin (CALR) frameshift mutations represent the second cause of myeloproliferative neoplasms (MPN). In healthy cells, CALR transiently and non-specifically interacts with immature N-glycosylated proteins through its N-terminal domain. Conversely, CALR frameshift mutants turn into rogue cytokines by stably and specifically interacting with the Thrombopoietin Receptor (TpoR), inducing its constitutive activation. Here, we identify the basis of the acquired specificity of CALR mutants for TpoR and define the mechanisms by which complex formation triggers TpoR dimerization and activation. Our work reveals that CALR mutant C-terminus unmasks CALR N-terminal domain, rendering it more accessible to bind immature N-glycans on TpoR. We further find that the basic mutant C-terminus is partially α-helical and define how its α-helical segment concomitantly binds acidic patches of TpoR extracellular domain and induces dimerization of both CALR mutant and TpoR. Finally, we propose a model of the tetrameric TpoR-CALR mutant complex and identify potentially targetable sites.
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Affiliation(s)
- Nicolas Papadopoulos
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
| | - Audrey Nédélec
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
| | - Allison Derenne
- Spectralys Biotech SRL, rue Auguste Piccard 48, 6041, Gosselies, Belgium
| | - Teodor Asvadur Şulea
- Department of Bioinformatics and Structural Biochemistry, Institute of Biochemistry of the Romanian Academy, Splaiul Independentei 296, Bucharest, 060031, Romania
| | - Christian Pecquet
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
| | - Ilyas Chachoua
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
- Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
| | - Gaëlle Vertenoeil
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
| | - Thomas Tilmant
- Mass Spectrometry Laboratory, MolSys Research Unit, Universiy of Liège, 4000, Liège, Belgium
| | - Andrei-Jose Petrescu
- Department of Bioinformatics and Structural Biochemistry, Institute of Biochemistry of the Romanian Academy, Splaiul Independentei 296, Bucharest, 060031, Romania
| | - Gabriel Mazzucchelli
- Mass Spectrometry Laboratory, MolSys Research Unit, Universiy of Liège, 4000, Liège, Belgium
| | - Bogdan I Iorga
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, Gif-sur-Yvette, France
| | - Didier Vertommen
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
- de Duve Institute and MASSPROT platform, Brussels, Belgium
| | - Stefan N Constantinescu
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium.
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium.
- Walloon Excelence in Life Sciences and Biotechnology, WELBIO, avenue Pasteur, 6, 1300, Wavre, Belgium.
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, Oxford University, Oxford, UK.
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21
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Efimova AA, Popov AS, Kazantsev AV, Semenyuk PI, Le-Deygen IM, Lukashev NV, Yaroslavov AA. pH-Sensitive Liposomes with Embedded 3-(isobutylamino)cholan-24-oic Acid: What Is the Possible Mechanism of Fast Cargo Release? Membranes (Basel) 2023; 13:407. [PMID: 37103834 PMCID: PMC10141028 DOI: 10.3390/membranes13040407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 03/28/2023] [Accepted: 03/31/2023] [Indexed: 06/19/2023]
Abstract
pH-sensitive liposomes have great potential for biomedical applications, in particular as nanocontainers for the delivery of biologically active compounds to specific areas of the human body. In this article, we discuss the possible mechanism of fast cargo release from a new type of pH-sensitive liposomes with embedded ampholytic molecular switch (AMS, 3-(isobutylamino)cholan-24-oic acid) with carboxylic anionic groups and isobutylamino cationic ones attached to the opposite ends of the steroid core. AMS-containing liposomes demonstrated the rapid release of the encapsulated substance when altering the pH of an outer solution, but the exact mechanism of the switch action has not yet been accurately determined. Here, we report on the details of fast cargo release based on the data obtained using ATR-FTIR spectroscopy as well as atomistic molecular modeling. The findings of this study are relevant to the potential application of AMS-containing pH-sensitive liposomes for drug delivery.
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Affiliation(s)
- Anna A. Efimova
- Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
| | - Anton S. Popov
- Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
| | - Alexey V. Kazantsev
- Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
| | - Pavel I. Semenyuk
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, Leninkie Gory 1/40, 119992 Moscow, Russia
| | - Irina M. Le-Deygen
- Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
| | - Nikolay V. Lukashev
- Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
| | - Alexander A. Yaroslavov
- Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
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22
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Klein S, Golani G, Lolicato F, Lahr C, Beyer D, Herrmann A, Wachsmuth-Melm M, Reddmann N, Brecht R, Hosseinzadeh M, Kolovou A, Makroczyova J, Peterl S, Schorb M, Schwab Y, Brügger B, Nickel W, Schwarz US, Chlanda P. IFITM3 blocks influenza virus entry by sorting lipids and stabilizing hemifusion. Cell Host Microbe 2023; 31:616-633.e20. [PMID: 37003257 DOI: 10.1016/j.chom.2023.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 11/15/2022] [Accepted: 03/06/2023] [Indexed: 04/03/2023]
Abstract
Interferon-induced transmembrane protein 3 (IFITM3) inhibits the entry of numerous viruses through undefined molecular mechanisms. IFITM3 localizes in the endosomal-lysosomal system and specifically affects virus fusion with target cell membranes. We found that IFITM3 induces local lipid sorting, resulting in an increased concentration of lipids disfavoring viral fusion at the hemifusion site. This increases the energy barrier for fusion pore formation and the hemifusion dwell time, promoting viral degradation in lysosomes. In situ cryo-electron tomography captured IFITM3-mediated arrest of influenza A virus membrane fusion. Observation of hemifusion diaphragms between viral particles and late endosomal membranes confirmed hemifusion stabilization as a molecular mechanism of IFITM3. The presence of the influenza fusion protein hemagglutinin in post-fusion conformation close to hemifusion sites further indicated that IFITM3 does not interfere with the viral fusion machinery. Collectively, these findings show that IFITM3 induces lipid sorting to stabilize hemifusion and prevent virus entry into target cells.
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Affiliation(s)
- Steffen Klein
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Gonen Golani
- BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany; Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Fabio Lolicato
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany; Department of Physics, University of Helsinki, Helsinki, Finland
| | - Carmen Lahr
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Daniel Beyer
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Alexia Herrmann
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Moritz Wachsmuth-Melm
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Nina Reddmann
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Romy Brecht
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Mehdi Hosseinzadeh
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Androniki Kolovou
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Jana Makroczyova
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Sarah Peterl
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Martin Schorb
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Yannick Schwab
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Britta Brügger
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Ulrich S Schwarz
- BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany; Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Petr Chlanda
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany.
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23
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Ermakova EA, Kurbanov RK. Interaction of Uperin Peptides with Model Membranes: Molecular Dynamics Study. Membranes (Basel) 2023; 13:370. [PMID: 37103797 PMCID: PMC10146956 DOI: 10.3390/membranes13040370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/13/2023] [Accepted: 03/20/2023] [Indexed: 06/19/2023]
Abstract
The interaction of antimicrobial and amyloid peptides with cell membranes is a critical step in their activities. Peptides of the uperin family obtained from the skin secretion of Australian amphibians demonstrate antimicrobial and amyloidogenic properties. All-atomic molecular dynamics and an umbrella sampling approach were used to study the interaction of uperins with model bacterial membrane. Two stable configurations of peptides were found. In the bound state, the peptides in helical form were located right under the head group region in parallel orientation with respect to the bilayer surface. Stable transmembrane configuration was observed for wild-type uperin and its alanine mutant in both alpha-helical and extended unstructured forms. The potential of mean force characterized the process of peptide binding from water to the lipid bilayer and its insertion into the membrane, and revealed that the transition of uperins from the bound state to the transmembrane position was accompanied by the rotation of peptides and passes through the energy barrier of 4-5 kcal/mol. Uperins have a weak effect on membrane properties.
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24
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Wurl A, M. Ferreira T. Atomistic MD Simulations of
n
‐Alkanes in a Phospholipid Bilayer: CHARMM36 versus Slipids. MACROMOL THEOR SIMUL 2023. [DOI: 10.1002/mats.202200078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Affiliation(s)
- Anika Wurl
- NMR group ‐ Institute for Physics Martin Luther University Halle‐Wittenberg Betty‐Heimann‐Str. 7 06120 Halle (Saale) Germany
| | - Tiago M. Ferreira
- NMR group ‐ Institute for Physics Martin Luther University Halle‐Wittenberg Betty‐Heimann‐Str. 7 06120 Halle (Saale) Germany
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25
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Nguyen PH, Derreumaux P. An S-Shaped Aβ42 Cross-β Hexamer Embedded into a Lipid Bilayer Reveals Membrane Disruption and Permeability. ACS Chem Neurosci 2023; 14:936-946. [PMID: 36757886 DOI: 10.1021/acschemneuro.2c00785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
Abstract
The interactions of amyloid oligomers with membranes are known to contribute to cellular toxicity. Numerous in vitro experimental studies reported on the insertion of oligomers of different sizes that can induce cell membrane disruption, extract lipids, and form ion-permeable transmembrane pores. The current repertoire of amyloid-beta (Aβ) membrane-inserted folds that was subject to high-resolution structure NMR spectroscopy and computer simulations is devoid of any cross-β fibrillar structure. In this study, we explored the dynamics of an S-shaped Aβ42 cross-β hexamer model inserted into a lipid bilayer membrane by two atomistic molecular dynamics simulations. The initial model is characterized by the hydrophobic residues at the central hydrophobic core (residues 17-21, CHC) and the C-terminus (residues 30-42) embedded into the membrane. We observed major structural secondary, tertiary, and quaternary rearrangements leading to two distinct species, hexamer and two trimers, accompanied by membrane disruption and water permeation. The simulations show that some configurations, but not the majority, have the CHC and C-terminus hydrophobic residues exposed to the solvent. Overall, our computational results offer new perspectives to understand the relationship between Aβ42 assemblies and membrane permeability.
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Affiliation(s)
- Phuong H Nguyen
- CNRS, UPR 9080, Laboratoire de Biochimie Théorique, Fondation Edmond de Rothschild, Université Paris Cité, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Philippe Derreumaux
- CNRS, UPR 9080, Laboratoire de Biochimie Théorique, Fondation Edmond de Rothschild, Université Paris Cité, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France.,Institut Universitaire de France (IUF), 75005 Paris, France
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26
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Barredo PA, Balanay MP. Recent Advances in Molecular Dynamics Simulations of Tau Fibrils and Oligomers. Membranes (Basel) 2023; 13:277. [PMID: 36984665 PMCID: PMC10052016 DOI: 10.3390/membranes13030277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 02/23/2023] [Accepted: 02/24/2023] [Indexed: 06/18/2023]
Abstract
The study of tau protein aggregation and interactions with other molecules or solvents using molecular dynamics simulations (MDs) is of interest to many researchers to propose new mechanism-based therapeutics for neurodegenerative diseases such as Alzheimer's disease, Pick's disease, chronic traumatic encephalopathy, and other tauopathies. In this review, we present recent MD simulation studies of tau oligomers and fibrils such as tau-NPK, tau-PHF, tau-K18, and tau-R3-R4 monomers and dimers. All-atom simulations by replica exchange MDs and coarse-grained MDs in lipid bilayers and in solution were used. The simulations revealed different mechanisms in the binding of tau in bilayers and in solutions, depending on the peptide size. Phosphorylation is also an important factor in MD simulations. The use of steered MDs was also included to simulate the dissociation of tau fibrils. The exponential improvement in the computing power of computers has led to an increasing number of scientists and engineers using a cost-effective, high-performance computing platform to study how the tau protein interacts and the effects of changing its structure, such as the phosphorylation of tau fibrils.
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Affiliation(s)
- Prechiel A. Barredo
- Department of Chemistry, Mindanao State University, Marawi City 9700, Philippines
| | - Mannix P. Balanay
- Department of Chemistry, Nazarbayev University, Astana 010000, Kazakhstan
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27
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Abstract
The cyclopropanation of unsaturated lipid acyl chains of some bacterial cell membranes is an important survival strategy to protect the same against drastic cooling. To elucidate the role of cyclopropane ring-containing lipids, we have simulated the lipid membrane of Escherichia coli (E. coli) and two modified membranes by replacing the cyclopropane rings with either single or double bonds at widely different temperatures. It has been observed that the cyclopropane rings provide more rigid kinks in the lipid acyl chain compared to the double bonds and therefore further reduce the packing density of the membrane and subsequently enhance the membrane fluidity at low temperatures. They also inhibit the close packing of other lipids and deleterious phase separation by strongly interacting with them. Therefore, this study has explained why E. coli bacterial strain, susceptible to freezing environments, relies on the cyclopropanation of an unsaturated chain.
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Affiliation(s)
- Archita Maiti
- Department of Chemistry, Indian Institute of Technology Patna, Patna, Bihar 801106, India
| | - Abhay Kumar
- Department of Chemistry, Indian Institute of Technology Patna, Patna, Bihar 801106, India
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28
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Wang W, Wu Z, Dietschreit JCB, Gómez-Bombarelli R. Learning pair potentials using differentiable simulations. J Chem Phys 2023; 158:044113. [PMID: 36725529 DOI: 10.1063/5.0126475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Learning pair interactions from experimental or simulation data is of great interest for molecular simulations. We propose a general stochastic method for learning pair interactions from data using differentiable simulations (DiffSim). DiffSim defines a loss function based on structural observables, such as the radial distribution function, through molecular dynamics (MD) simulations. The interaction potentials are then learned directly by stochastic gradient descent, using backpropagation to calculate the gradient of the structural loss metric with respect to the interaction potential through the MD simulation. This gradient-based method is flexible and can be configured to simulate and optimize multiple systems simultaneously. For example, it is possible to simultaneously learn potentials for different temperatures or for different compositions. We demonstrate the approach by recovering simple pair potentials, such as Lennard-Jones systems, from radial distribution functions. We find that DiffSim can be used to probe a wider functional space of pair potentials compared with traditional methods like iterative Boltzmann inversion. We show that our methods can be used to simultaneously fit potentials for simulations at different compositions and temperatures to improve the transferability of the learned potentials.
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Affiliation(s)
- Wujie Wang
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, USA
| | - Zhenghao Wu
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Johannes C B Dietschreit
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, USA
| | - Rafael Gómez-Bombarelli
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, USA
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29
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Pradhan R, Panigrahi S, Sahu PK. Conformational Search for the Building Block of Proteins Based on the Gradient Gravitational Search Algorithm (ConfGGS) Using Force Fields: CHARMM, AMBER, and OPLS-AA. J Chem Inf Model 2023; 63:670-690. [PMID: 36625780 DOI: 10.1021/acs.jcim.2c01398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Proteins are linear polymers built from a repertoire of 20 different amino acids, which are considered building blocks of proteins. The diversity and versatility of these 20 building blocks with regard to their conformations are key to adopting three-dimensional structures that facilitate proteins to undergo important mechanistic biological processes in living systems. The present investigation reports a conformational search of 20 different amino acids, building blocks of proteins, using three different force fields, CHARMM, AMBER, and OPLS-AA, implemented in the gradient gravitational search algorithm. The search technique (ConfGGS) includes the contribution from both bonded and nonbonded terms using Cartesian coordinates. The efficiency of such conformational searches has also been compared with other optimization algorithms: DE/Best, DE/Rand, and PSO algorithms with respect to computational time and accuracy based on the minimum number of iteration steps and computed lowest mean absolute error (MAE) and mean standard deviation (MSD) values for dihedral angles of respective near-optimal structures. Moreover, the ConfGGS technique has also been extended to an ordered protein fragment (PQITL) extracted from HIV-1 protease (PDB ID: 1YTH), an intrinsically disordered protein fragment, i.e., an amyloid-forming segment (AVVTGVTAV), from the NAC domain of Parkinson's disease protein α-synuclein, residues 69-77 (PDB ID: 4RIK), the experimental NMR atomic-resolution structure of α-synuclein fibrils (PDB ID: 2N0A), and a disulfide bond-containing protein fragment sequence (PCYGWPVCY), residues 59-67 (PDB ID: 6Y4F) toward structure prediction as a close homologue compared with experimental accuracy, using the CHARMM force field. The MolProbity validation results for the protein fragment (PQITL) obtained by ConfGGS/CHARMM are in better agreement with the native protein fragment structure of HIV-1 protease (PDB ID: 1YTH). Furthermore, the computed results have also been compared with the coordinates obtained from the AlphaFold network.
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Affiliation(s)
- Rojalin Pradhan
- Computational Modeling Research Laboratory, School of Chemistry (Autonomous), Sambalpur University, Jyoti Vihar, Burla768019, India
| | - Sibarama Panigrahi
- Computational Modeling Research Laboratory, School of Chemistry (Autonomous), Sambalpur University, Jyoti Vihar, Burla768019, India
- Department of Computer Science and Engineering, Sambalpur University Institute of Information Technology, Jyoti Vihar, Burla768019, India
| | - Prabhat K Sahu
- Computational Modeling Research Laboratory, School of Chemistry (Autonomous), Sambalpur University, Jyoti Vihar, Burla768019, India
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30
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Bouquiaux C, Castet F, Champagne B. Influence of the Nature of the Lipid Building Blocks on the Second-Order Nonlinear Optical Responses of an Embedded Di-8-ANEPPS Probe. J Phys Chem B 2023; 127:528-541. [PMID: 36606294 DOI: 10.1021/acs.jpcb.2c08093] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The extensive collection of lipids found in cell membranes is justified by the fact that each lipid contributes to their overall structure, dynamics, and properties and so to the biological processes taking place within them. It also showcases that, in order to deepen our understanding of membranes, we need to have a tool to differentiate lipid bilayers of varying composition. In this work, we investigate a suite of single-component saturated glycerophospholipids varying only in their headgroup structure by analyzing the second harmonic generation (SHG) nonlinear optical (NLO) response of a probe, di-8-ANEPPS, embedded into the membranes. The seven hydrophilic heads chosen (phosphatidylcholine (PC), phosphatidylethanolamine (PE), diaglycerol (GL), phosphatidylserine (PS), phosphatidylglycerol (PG), phosphatidylinositol (PI), and phosphatidyc acid (PA)) represent all the major headgroups that are part of mammalian plasma membranes and provide an assortment of neutral, zwiterrionic, and charged species. First, molecular dynamics simulations revealed that the lipidic arrangement is strongly sensitive to the nature of the hydrophilic head and less to the variety in the hydrophobic region. Membranes exhibiting drastically opposite structural properties can be pointed out: 1,2-dihexadecanoyl-rac-glycerol (DPGL) is the thickest and most ordered and aligned system, whereas 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) (DPPG) is thinnest and least ordered and aligned system. The structural analyses are then confronted with the molecular NLO responses, β, computed at the time-dependent density functional theory (TDDFT) level. As the orientation of the chromophore is impacted by the various degrees of order within the lipid bilayers, the diagonal component of the β tensor parallel to the bilayer normal, βZZZ, is as well. In the end, this computational approach provides insights into the link between lipid building blocks and the NLO responses of the embedded dye.
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Affiliation(s)
- Charlotte Bouquiaux
- University of Namur, Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, rue de Bruxelles, 61, B-5000Namur, Belgium
| | - Frédéric Castet
- University of Bordeaux, Institut des Sciences Moléculaires, UMR 5255 CNRS, cours de la Libération 351, F-33405 CedexTalence, France
| | - Benoît Champagne
- University of Namur, Theoretical Chemistry Lab, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, rue de Bruxelles, 61, B-5000Namur, Belgium
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31
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Andrews B, Ruggiero T, Urbanc B. How do salt and lipids affect conformational dynamics of Aβ42 monomers in water? Phys Chem Chem Phys 2023; 25:2566-2583. [PMID: 36602150 DOI: 10.1039/d2cp05044g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
It is well established that amyloid β-protein (Aβ) self-assembly is involved in triggering of Alzheimer's disease. On the other hand, evidence of physiological function of Aβ interacting with lipids has only begun to emerge. Details of Aβ-lipid interactions, which may underlie physiological and pathological activities of Aβ, are not well understood. Here, the effects of salt and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipids on conformational dynamics of Aβ42 monomer in water are examined by all-atom molecular dynamics (MD). We acquired six sets of 250 ns long MD trajectories for each of the three lipid concentrations (0, 27, and 109 mM) in the absence and presence of 150 mM salt. Ten replica trajectories per set are used to enhance sampling of Aβ42 conformational space. We show that salt facilitates long-range tertiary contacts in Aβ42, resulting in more compact Aβ42 conformations. By contrast, addition of lipids results in lipid-concentration dependent Aβ42 unfolding concomitant with enhanced stability of the turn in the A21-A30 region. At the high lipid concentration, salt enables the N-terminal region of Aβ42 to form long-range tertiary contacts and interact with lipids, which results in formation of a parallel β-strand. Aβ42 forms stable lipid-protein complexes whereby the protein is adhered to the lipid cluster rather than embedded into it. We propose that the inability of Aβ42 monomer to get embedded into the lipid cluster may be important for facilitating repair of leaks in the blood-brain barrier without penetrating and damaging cellular membranes.
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Affiliation(s)
- Brian Andrews
- Department of Physics, Drexel University, Philadelphia, Pennsylvania, USA.
| | - Thomas Ruggiero
- Department of Physics, Drexel University, Philadelphia, Pennsylvania, USA.
| | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia, Pennsylvania, USA.
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32
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Madin OC, Shirts MR. Using physical property surrogate models to perform accelerated multi-fidelity optimization of force field parameters †. Digit Discov 2023; 2:828-847. [PMCID: PMC10259372 DOI: 10.1039/d2dd00138a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 04/28/2023] [Indexed: 06/14/2023]
Abstract
Accurate representations of van der Waals dispersion–repulsion interactions play an important role in high-quality molecular dynamics simulations. Training the force field parameters used in the Lennard Jones (LJ) potential typically used to represent these interactions is challenging, generally requiring adjustment based on simulations of macroscopic physical properties. The large computational expense of these simulations, especially when many parameters must be trained simultaneously, limits the size of training data set and number of optimization steps that can be taken, often requiring modelers to perform optimizations within a local parameter region. To allow for more global LJ parameter optimization against large training sets, we introduce a multi-fidelity optimization technique which uses Gaussian process surrogate modeling to build inexpensive models of physical properties as a function of LJ parameters. This approach allows for fast evaluation of approximate objective functions, greatly accelerating searches over parameter space and enabling the use of optimization algorithms capable of searching more globally. In this study, we use an iterative framework which performs global optimization with differential evolution at the surrogate level, followed by validation at the simulation level and surrogate refinement. Using this technique on two previously studied training sets, containing up to 195 physical property targets, we refit a subset of the LJ parameters for the OpenFF 1.0.0 (Parsley) force field. We demonstrate that this multi-fidelity technique can find improved parameter sets compared to a purely simulation-based optimization by searching more broadly and escaping local minima. Additionally, this technique often finds significantly different parameter minima that have comparably accurate performance. In most cases, these parameter sets are transferable to other similar molecules in a test set. Our multi-fidelity technique provides a platform for rapid, more global optimization of molecular models against physical properties, as well as a number of opportunities for further refinement of the technique. We present a multi-fidelity method for optimizing nonbonded force field parameters against physical property data. Leveraging fast surrogate models, we accelerate the parameter search and find novel solutions that improve force field performance.![]()
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Affiliation(s)
- Owen C. Madin
- Department of Chemical & Biological Engineering, University of Colorado BoulderBoulderCOUSA80309
| | - Michael R. Shirts
- Department of Chemical & Biological Engineering, University of Colorado BoulderBoulderCOUSA80309
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33
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Roesel D, Eremchev M, Poojari CS, Hub JS, Roke S. Ion-Induced Transient Potential Fluctuations Facilitate Pore Formation and Cation Transport through Lipid Membranes. J Am Chem Soc 2022; 144:23352-23357. [PMID: 36521841 PMCID: PMC9801421 DOI: 10.1021/jacs.2c08543] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Unassisted ion transport through lipid membranes plays a crucial role in many cell functions without which life would not be possible, yet the precise mechanism behind the process remains unknown due to its molecular complexity. Here, we demonstrate a direct link between membrane potential fluctuations and divalent ion transport. High-throughput wide-field non-resonant second harmonic (SH) microscopy of membrane water shows that membrane potential fluctuations are universally found in lipid bilayer systems. Molecular dynamics simulations reveal that such variations in membrane potential reduce the free energy cost of transient pore formation and increase the ion flux across an open pore. These transient pores can act as conduits for ion transport, which we SH image for a series of divalent cations (Cu2+, Ca2+, Ba2+, Mg2+) passing through giant unilamellar vesicle (GUV) membranes. Combining the experimental and computational results, we show that permeation through pores formed via an ion-induced electrostatic field is a viable mechanism for unassisted ion transport.
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Affiliation(s)
- David Roesel
- Laboratory
for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI),
School of Engineering (STI), École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Maksim Eremchev
- Laboratory
for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI),
School of Engineering (STI), École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Chetan S. Poojari
- Theoretical
Physics and Center for Biophysics, Saarland
University, 66123 Saarbrücken, Germany
| | - Jochen S. Hub
- Theoretical
Physics and Center for Biophysics, Saarland
University, 66123 Saarbrücken, Germany,
| | - Sylvie Roke
- Laboratory
for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI),
School of Engineering (STI), École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland,Institute
of Materials Science and Engineering (IMX), School of Engineering
(STI), École Polytechnique Fédérale
de Lausanne (EPFL), CH-1015 Lausanne, Switzerland,Lausanne
Centre for Ultrafast Science, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland,
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34
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Megariotis G, Mikaelian G, Avramopoulos A, Romanos N, Theodorou DN. Molecular simulations of fluoxetine in hydrated lipid bilayers, as well as in aqueous solutions containing β-cyclodextrin. J Mol Graph Model 2022; 117:108305. [PMID: 35987186 DOI: 10.1016/j.jmgm.2022.108305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 07/25/2022] [Accepted: 08/06/2022] [Indexed: 01/14/2023]
Abstract
Fluoxetine, which is a well-known antidepressant drug, is studied in hydrated cholesterol-free and cholesterol-containing lipid bilayers through unbiased and biased atomistic molecular dynamics simulations. The latter are conducted for the calculation of the potential of mean force (PMF) of fluoxetine along an axis perpendicular to the two leaflets of the bilayer. The PMF indicates that the drug prefers to reside inside the lipid phase and allows us to calculate important thermodynamic properties, such as the Gibbs energy difference of partitioning from the water to the lipid phase and the Gibbs energy barrier for hopping events between the two leaflets of the bilayer. The results from the biased simulations are in accord with the mass density profiles calculated from the unbiased simulations. Moreover, we estimate the effect of fluoxetine mole fraction on the order parameters of the lipid alkyl chains and on the area per lipid. It is also found that fluoxetine forms a hydrogen bond network with lipids and water molecules penetrating into the lipid phase. In addition, fluoxoetine is studied in detail in aqueous solutions containing β-cyclodextrin. It is observed from unbiased molecular dynamics simulations that the two aforementioned molecules form a noncovalent complex spontaneously and the calculated binding free energy is in agreement with the literature.
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Affiliation(s)
- Grigorios Megariotis
- School of Chemical Engineering, National Technical University of Athens (NTUA), 9 Heroon Polytechniou Street, Zografou Campus, Athens, GR, 15780, Greece.
| | - Georgios Mikaelian
- School of Chemical Engineering, National Technical University of Athens (NTUA), 9 Heroon Polytechniou Street, Zografou Campus, Athens, GR, 15780, Greece
| | - Aggelos Avramopoulos
- Department of Physics, University of Thessaly, 3rd Km Old National Road Lamia Athens, Lamia, GR, 35100, Greece
| | - Nikolaos Romanos
- School of Chemical Engineering, National Technical University of Athens (NTUA), 9 Heroon Polytechniou Street, Zografou Campus, Athens, GR, 15780, Greece
| | - Doros N Theodorou
- School of Chemical Engineering, National Technical University of Athens (NTUA), 9 Heroon Polytechniou Street, Zografou Campus, Athens, GR, 15780, Greece
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35
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Oh S, Stix R, Zhou W, Faraldo-gómez JD, Hite RK. Mechanism of 4-aminopyridine inhibition of the lysosomal channel TMEM175. Proc Natl Acad Sci U S A 2022; 119. [PMID: 36279431 PMCID: PMC9636928 DOI: 10.1073/pnas.2208882119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transmembrane protein 175 (TMEM175) is an evolutionarily distinct lysosomal cation channel whose mutation is associated with the development of Parkinson’s disease. Here, we present a cryoelectron microscopy structure and molecular simulations of TMEM175 bound to 4-aminopyridine (4-AP), the only known small-molecule inhibitor of TMEM175 and a broad K
+
channel inhibitor, as well as a drug approved by the Food and Drug Administration against multiple sclerosis. The structure shows that 4-AP, whose mode of action had not been previously visualized, binds near the center of the ion conduction pathway, in the open state of the channel. Molecular dynamics simulations reveal that this binding site is near the middle of the transmembrane potential gradient, providing a rationale for the voltage-dependent dissociation of 4-AP from TMEM175. Interestingly, bound 4-AP rapidly switches between three predominant binding poses, stabilized by alternate interaction patterns dictated by the twofold symmetry of the channel. Despite this highly dynamic binding mode, bound 4-AP prevents not only ion permeation but also water flow. Together, these studies provide a framework for the rational design of novel small-molecule inhibitors of TMEM175 that might reveal the role of this channel in human lysosomal physiology both in health and disease.
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36
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Sung MW, Driggers CM, Mostofian B, Russo JD, Patton BL, Zuckerman DM, Shyng SL. Ligand-mediated Structural Dynamics of a Mammalian Pancreatic K ATP Channel. J Mol Biol 2022; 434:167789. [PMID: 35964676 PMCID: PMC9618280 DOI: 10.1016/j.jmb.2022.167789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 07/22/2022] [Accepted: 08/09/2022] [Indexed: 11/16/2022]
Abstract
Regulation of pancreatic KATP channels involves orchestrated interactions of their subunits, Kir6.2 and SUR1, and ligands. Previously we reported KATP channel cryo-EM structures in the presence and absence of pharmacological inhibitors and ATP, focusing on the mechanisms by which inhibitors act as pharmacological chaperones of KATP channels (Martin et al., 2019). Here we analyzed the same cryo-EM datasets with a focus on channel conformational dynamics to elucidate structural correlates pertinent to ligand interactions and channel gating. We found pharmacological inhibitors and ATP enrich a channel conformation in which the Kir6.2 cytoplasmic domain is closely associated with the transmembrane domain, while depleting one where the Kir6.2 cytoplasmic domain is extended away into the cytoplasm. This conformational change remodels a network of intra- and inter-subunit interactions as well as the ATP and PIP2 binding pockets. The structures resolved key contacts between the distal N-terminus of Kir6.2 and SUR1's ABC module involving residues implicated in channel function and showed a SUR1 residue, K134, participates in PIP2 binding. Molecular dynamics simulations revealed two Kir6.2 residues, K39 and R54, that mediate both ATP and PIP2 binding, suggesting a mechanism for competitive gating by ATP and PIP2.
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Affiliation(s)
- Min Woo Sung
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, USA. https://twitter.com/MinWooSung5
| | - Camden M Driggers
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, USA
| | - Barmak Mostofian
- Department of Biomedical Engineering, School of Medicine, Oregon Health & Science University, Portland, OR, USA
| | - John D Russo
- Department of Biomedical Engineering, School of Medicine, Oregon Health & Science University, Portland, OR, USA
| | - Bruce L Patton
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, USA
| | - Daniel M Zuckerman
- Department of Biomedical Engineering, School of Medicine, Oregon Health & Science University, Portland, OR, USA.
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, USA.
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37
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Umegawa Y, Shimonishi T, Tsuchikawa H, Murata M. LnDOTA-d 8 , a versatile chemical-shift thermometer for 2 H solid-state NMR. Magn Reson Chem 2022; 60:1005-1013. [PMID: 35938541 DOI: 10.1002/mrc.5303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 08/03/2022] [Accepted: 08/05/2022] [Indexed: 06/15/2023]
Abstract
2 H solid-state nuclear magnetic resonance (NMR) is a method for examining the mobility and orientation of molecules in the field of biophysics. In studies on lipid bilayer membranes, 2 H NMR is often adopted to detect a phase transition from the gel to the liquid-crystal phase, which is observed as a change in spectral shape, and to evaluate the ordering of lipid alkyl chains using quadrupole coupling values. Because the mobility of membrane lipids is highly temperature dependent, precise temperature control is a prerequisite for evaluating the physical properties of membranes. Generally, NMR instruments monitor the temperature of the variable temperature (VT) gas. The temperature inside the sample tube and the VT gas match only when the heat generated by the radio frequency (rf) pulse emitted from the coil or magic angle spinning is significantly lower than the cooling capacity of the VT gas. In other words, the sample temperature inside the tube depends on the measurement method. Therefore, in this study, we took advantage of temperature-dependent changes in the chemical shift of a paramagnetic metal-ligand complex. We designed and synthesized a deuterated ligand complex and evaluated its temperature dependence as a thermometer for 2 H solid-state NMR spectroscopy. We chose Tb, Dy, Ho, and Er as the paramagnetic central metals. We then measured the 2 H NMR spectrum of each metal complex and confirmed the 2 H chemical shift to be temperature dependent. Furthermore, with the use of the thermometer molecule with Er, we succeeded in accurately evaluating the segmental melting of an alkyl chain in lipid bilayers with 0.1°C accuracy.
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Affiliation(s)
- Yuichi Umegawa
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
- JST ERATO, Lipid Active Structure Project and Project Research Center for Fundamental Science, Osaka University, Osaka, Japan
| | - Takeshi Shimonishi
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
- Faculty of Medicine, Oita University, Yufu, Oita, Japan
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
- JST ERATO, Lipid Active Structure Project and Project Research Center for Fundamental Science, Osaka University, Osaka, Japan
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38
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Erimban S, Daschakraborty S. Homeoviscous Adaptation of the Lipid Membrane of a Soil Bacterium Surviving under Diurnal Temperature Variation: A Molecular Simulation Perspective. J Phys Chem B 2022; 126:7638-7650. [PMID: 36166758 DOI: 10.1021/acs.jpcb.2c01359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A recent experiment has reported the lipidome remodeling of a soil-based plant-associated bacterium Methylobacterium extorquens due to diurnal temperature variations. The key adaptation strategy is the headgroup-specific remodeling of the acyl chain. To understand the idiosyncratic adaptation at the molecular level, we simulate the model membrane of the same bacterium using the reported lipidome compositions at four different experimental temperatures. We investigate the temperature-dependent packing density and fluidity of the membrane, the constancy of which is key to the homeoviscous adaptation. The results show that complex lipidome remodeling approximately preserves membrane properties under heat and cold stress. The headgroup-specific remodeling of the acyl chain serves to fine-tune the packing density and fluidity of the membrane at different temperatures. While lipids with strongly interacting headgroups are more abundant at higher temperatures, the lipidome is more dominated by lipids with weaker interacting headgroups at lower temperatures. This adaptation alleviates lipid membrane disruption caused by heat and cold stress. This study provides a molecular picture of the homeoviscous adaptation of the realistic lipid membrane of a soil-based bacterium.
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Affiliation(s)
- Shakkira Erimban
- Department of Chemistry, Indian Institute of Technology, Patna, Bihar 801106, India
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39
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Kognole AA, Aytenfisu AH, MacKerell AD. Extension of the CHARMM Classical Drude Polarizable Force Field to N- and O-Linked Glycopeptides and Glycoproteins. J Phys Chem B 2022; 126:6642-6653. [PMID: 36005290 PMCID: PMC9463114 DOI: 10.1021/acs.jpcb.2c04245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Molecular dynamic simulations are an effective tool to study complex molecular systems and are contingent upon the availability of an accurate and reliable molecular mechanics force field. The Drude polarizable force field, which allows for the explicit treatment of electronic polarization in a computationally efficient fashion, has been shown to reproduce experimental properties that were difficult or impossible to reproduce with the CHARMM additive force field, including peptide folding cooperativity, RNA hairpin structures, and DNA base flipping. Glycoproteins are essential components of glycoconjugate vaccines, antibodies, and many pharmaceutically important molecules, and an accurate polarizable force field that includes compatibility between the protein and carbohydrate aspect of the force field is essential to study these types of systems. In this work, we present an extension of the Drude polarizable force field to glycoproteins, including both N- and O-linked species. Parameter optimization focused on the dihedral terms using a reweighting protocol targeting NMR solution J-coupling data for model glycopeptides. Validation of the model include eight model glycopeptides and four glycoproteins with multiple N- and O-linked glycosylations. The new glycoprotein carbohydrate force field can be used in conjunction with the remainder of Drude polarizable force field through a variety of MD simulation programs including GROMACS, OPENMM, NAMD, and CHARMM and may be accessed through the Drude Prepper module in the CHARMM-GUI.
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Affiliation(s)
| | | | - Alexander D. MacKerell
- Computer-Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, United States
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40
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Rózsa ZB, Thangaraj R, Viskolcz B, Szőri M. Foreseeing the future of green Technology. Molecular dynamic investigation on passive membrane penetration by the products of the CO2 and 1,3-butadiene reaction. J Mol Liq 2022; 361:119581. [DOI: 10.1016/j.molliq.2022.119581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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41
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Kwiecińska K, Stachowicz-kuśnierz A, Korchowiec B, Roman M, Kwiatek WM, Jagusiak A, Roterman I, Korchowiec J. Congo Red as a Supramolecular Carrier System for Doxorubicin: An Approach to Understanding the Mechanism of Action. Int J Mol Sci 2022; 23:8935. [PMID: 36012200 PMCID: PMC9408855 DOI: 10.3390/ijms23168935] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 08/06/2022] [Accepted: 08/09/2022] [Indexed: 11/17/2022] Open
Abstract
The uptake and distribution of doxorubicin in the MCF7 line of breast-cancer cells were monitored by Raman measurements. It was demonstrated that bioavailability of doxorubicin can be significantly enhanced by applying Congo red. To understand the mechanism of doxorubicin delivery by Congo red supramolecular carriers, additional monolayer measurements and molecular dynamics simulations on model membranes were undertaken. Acting as molecular scissors, Congo red particles cut doxorubicin aggregates and incorporated them into small-sized Congo red clusters. The mixed doxorubicin/Congo red clusters were adsorbed to the hydrophilic part of the model membrane. Such behavior promoted transfer through the membrane.
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42
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Abstract
Studies indicate a crucial cell membrane role in the antibiotic resistance of Staphylococcus aureus. To simulate its membrane structure and dynamics, a complex molecular-scale computational representation of the S. aureus lipid bilayer was developed. Phospholipid types and their amounts were optimized by reverse Monte Carlo to represent characterization data from the literature, leading to 19 different phospholipid types that combine three headgroups [phosphatidylglycerol, lysyl-phosphatidylglycerol (LPG), and cardiolipin] and 10 tails, including iso- and anteiso-branched saturated chains. The averaged lipid bilayer thickness was 36.7 Å, and area per headgroup was 67.8 Å2. Phosphorus and nitrogen density profiles showed that LPG headgroups tended to be bent and oriented more parallel to the bilayer plane. The water density profile showed that small amounts reached the membrane center. Carbon density profiles indicated hydrophobic interactions for all lipids in the middle of the bilayer. Bond vector order parameters along each tail demonstrated different C-H ordering even within distinct lipids of the same type; however, all tails followed similar trends in average order parameter. These complex simulations further revealed bilayer insights beyond those attainable with monodisperse, unbranched lipids. Longer tails often extended into the opposite leaflet. Carbon at and beyond a branch showed significantly decreased ordering compared to carbon in unbranched tails; this feature arose in every branched lipid. Diverse tail lengths distributed these disordered methyl groups throughout the middle third of the bilayer. Distributions in mobility and ordering reveal diverse properties that cannot be obtained with monodisperse lipids.
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Affiliation(s)
- Faramarz Joodaki
- Department of Chemical Engineering, University of Rhode Island, 360 Fascitelli Center for Advanced Engineering, Kingston, Rhode Island 02881, United States
| | - Lenore M Martin
- Department of Cell and Molecular Biology, University of Rhode Island, 120 Flagg Road, Kingston, Rhode Island 02881, United States
| | - Michael L Greenfield
- Department of Chemical Engineering, University of Rhode Island, 360 Fascitelli Center for Advanced Engineering, Kingston, Rhode Island 02881, United States
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43
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Schäffler M, Khaled M, Strodel B. ATRANET – Automated generation of transition networks for the structural characterization of intrinsically disordered proteins. Methods 2022; 206:18-26. [DOI: 10.1016/j.ymeth.2022.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 10/16/2022] Open
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44
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Brinkmann BW, Singhal A, Sevink GJA, Neeft L, Vijver MG, Peijnenburg WJGM. Predicted Adsorption Affinity for Enteric Microbial Metabolites to Metal and Carbon Nanomaterials. J Chem Inf Model 2022; 62:3589-3603. [PMID: 35876029 PMCID: PMC9364324 DOI: 10.1021/acs.jcim.2c00492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Ingested nanomaterials are exposed to many metabolites
that are
produced, modified, or regulated by members of the enteric microbiota.
The adsorption of these metabolites potentially affects the identity,
fate, and biodistribution of nanomaterials passing the gastrointestinal
tract. Here, we explore these interactions using in silico methods,
focusing on a concise overview of 170 unique enteric microbial metabolites
which we compiled from the literature. First, we construct quantitative
structure–activity relationship (QSAR) models to predict their
adsorption affinity to 13 metal nanomaterials, 5 carbon nanotubes,
and 1 fullerene. The models could be applied to predict log k values for 60 metabolites and were particularly applicable
to ‘phenolic, benzoyl and phenyl derivatives’, ‘tryptophan
precursors and metabolites’, ‘short-chain fatty acids’,
and ‘choline metabolites’. The correlations of these
predictions to biological surface adsorption index descriptors indicated
that hydrophobicity-driven interactions contribute most to the overall
adsorption affinity, while hydrogen-bond interactions and polarity/polarizability-driven
interactions differentiate the affinity to metal and carbon nanomaterials.
Next, we use molecular dynamics (MD) simulations to obtain direct
molecular information for a selection of vitamins that could not be
assessed quantitatively using QSAR models. This showed how large and
flexible metabolites can gain stability on the nanomaterial surface
via conformational changes. Additionally, unconstrained MD simulations
provided excellent support for the main interaction types identified
by QSAR analysis. Combined, these results enable assessing the adsorption
affinity for many enteric microbial metabolites quantitatively and
support the qualitative assessment of an even larger set of complex
and biologically relevant microbial metabolites to carbon and metal
nanomaterials.
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Affiliation(s)
- Bregje W Brinkmann
- Institute of Environmental Sciences (CML), Leiden University, P.O. Box 9518, 2300 RA Leiden, The Netherlands
| | - Ankush Singhal
- Leiden Institute of Chemistry (LIC), Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - G J Agur Sevink
- Leiden Institute of Chemistry (LIC), Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Lisette Neeft
- Institute of Environmental Sciences (CML), Leiden University, P.O. Box 9518, 2300 RA Leiden, The Netherlands
| | - Martina G Vijver
- Institute of Environmental Sciences (CML), Leiden University, P.O. Box 9518, 2300 RA Leiden, The Netherlands
| | - Willie J G M Peijnenburg
- Institute of Environmental Sciences (CML), Leiden University, P.O. Box 9518, 2300 RA Leiden, The Netherlands.,National Institute of Public Health and the Environment (RIVM), Center for Safety of Substances and Products, P.O. Box 1, 3720 BA Bilthoven, The Netherlands
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45
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Rangamani P. The many faces of membrane tension: Challenges across systems and scales. Biochim Biophys Acta Biomembr 2022; 1864:183897. [PMID: 35231438 DOI: 10.1016/j.bbamem.2022.183897] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 02/09/2022] [Accepted: 02/16/2022] [Indexed: 01/27/2023]
Abstract
Our understanding of the role of membrane tension in the field of membrane biophysics is rapidly evolving from a passive construct to an active player in a variety of cellular phenomena. Membrane tension has been shown to be a key regulator of many cellular processes ranging including trafficking, ion channel activation, and the invasion of red blood cells by malaria parasites. Recent experimental advances in cells, including the development of a fluorescent tension reporter, have shown that membrane tension is heterogeneous. In this mini-review, I summarize the recent advances in membrane tension measurements and discuss the contributions from different cellular constituents such as the cortical cytoskeleton. Then, I will explore how these different complexities can be considered in biophysical models of different scales. Finally, I will elaborate on the need for iterations between models and experiments as technologies in both fields advance to enable us to obtain critical insights into the physiological role of membrane tension as a critical component of mechanotransduction.
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Willegems K, Eldstrom J, Kyriakis E, Ataei F, Sahakyan H, Dou Y, Russo S, Van Petegem F, Fedida D. Structural and electrophysiological basis for the modulation of KCNQ1 channel currents by ML277. Nat Commun 2022; 13:3760. [PMID: 35768468 PMCID: PMC9243137 DOI: 10.1038/s41467-022-31526-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 06/17/2022] [Indexed: 01/10/2023] Open
Abstract
The KCNQ1 ion channel plays critical physiological roles in electrical excitability and K+ recycling in organs including the heart, brain, and gut. Loss of function is relatively common and can cause sudden arrhythmic death, sudden infant death, epilepsy and deafness. Here, we report cryogenic electron microscopic (cryo-EM) structures of Xenopus KCNQ1 bound to Ca2+/Calmodulin, with and without the KCNQ1 channel activator, ML277. A single binding site for ML277 was identified, localized to a pocket lined by the S4-S5 linker, S5 and S6 helices of two separate subunits. Several pocket residues are not conserved in other KCNQ isoforms, explaining specificity. MD simulations and point mutations support this binding location for ML277 in open and closed channels and reveal that prevention of inactivation is an important component of the activator effect. Our work provides direction for therapeutic intervention targeting KCNQ1 loss of function pathologies including long QT interval syndrome and seizures. KCNQ1 channels are active in heart, brain and gut. Functional loss causes epilepsy and sudden arrhythmic death. Here, authors describe a key activator drug binding site, explaining isoform and drug selectivity, and point the way for new drug design.
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Affiliation(s)
- Katrien Willegems
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada.,Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Efthimios Kyriakis
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Fariba Ataei
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Harutyun Sahakyan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes for Health, Bethesda, MD, USA
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Sophia Russo
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada.
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47
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Nguyen PH, Derreumaux P. Molecular Dynamics Simulations of the Tau Amyloid Fibril Core Dimer at the Surface of a Lipid Bilayer Model: I. In Alzheimer's Disease. J Phys Chem B 2022; 126:4849-4856. [PMID: 35759677 DOI: 10.1021/acs.jpcb.2c02836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A tau R3-R4 domain spanning residues 306-378 was shown to form an amyloid fibril core of a full-length tau in the brain of patients with Alzheimer's disease. Recently, we studied the dynamics of a tau R3-R4 monomer at the surface of a lipid bilayer model and revealed deep insertion of the amino acids spanning the PHF6 motif (residues 306-311) and its flanking residues. Here, we explore the membrane-associated conformational ensemble of a tau R3-R4 dimer by means of atomistic molecular dynamics. Similar to the monomer simulation, the R3-R4 dimer has the propensity to form β-hairpin-like conformation. Unlike the monomer, the dimer shows insertion of the C-terminal R4 region and transient adsorption of the PHF6 motif. Taken together, these results reveal the multiplicity of adsorption and insertion modes of tau into membranes depending on its oligomer size.
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Affiliation(s)
- Phuong H Nguyen
- CNRS, Université Paris Cité, UPR 9080, Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Philippe Derreumaux
- CNRS, Université Paris Cité, UPR 9080, Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild, 13 rue Pierre et Marie Curie, 75005 Paris, France.,Institut Universitaire de France (IUF), 75005 Paris, France
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48
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Stachowicz-Kuśnierz A, Korchowiec B, Rogalska E, Korchowiec J. The lung surfactant activity probed with molecular dynamics simulations. Adv Colloid Interface Sci 2022; 304:102659. [PMID: 35421637 DOI: 10.1016/j.cis.2022.102659] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 03/18/2022] [Accepted: 03/31/2022] [Indexed: 01/17/2023]
Abstract
The surface of pulmonary alveolar subphase is covered with a mixture of lipids and proteins. This lung surfactant plays a crucial role in lung functioning. It shows a complex phase behavior which can be altered by the interaction with third molecules such as drugs or pollutants. For studying multicomponent biological systems, it is of interest to couple experimental approach with computational modelling yielding atomic-scale information. Simple two, three, or four-component model systems showed to be useful for getting more insight in the interaction between lipids, lipids and proteins or lipids and proteins with drugs and impurities. These systems were studied theoretically using molecular dynamic simulations and experimentally by means of the Langmuir technique. A better understanding of the structure and behavior of lung surfactants obtained from this research is relevant for developing new synthetic surfactants for efficient therapies, and may contribute to public health protection.
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49
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Oh S, Marinelli F, Zhou W, Lee J, Choi HJ, Kim M, Faraldo-Gómez JD, Hite RK. Differential ion dehydration energetics explains selectivity in the non-canonical lysosomal K + channel TMEM175. eLife 2022; 11:75122. [PMID: 35608336 PMCID: PMC9129878 DOI: 10.7554/elife.75122] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 05/01/2022] [Indexed: 12/31/2022] Open
Abstract
Structures of the human lysosomal K+ channel transmembrane protein 175 (TMEM175) in open and closed states revealed a novel architecture lacking the canonical K+ selectivity filter motif present in previously known K+ channel structures. A hydrophobic constriction composed of four isoleucine residues was resolved in the pore and proposed to serve as the gate in the closed state, and to confer ion selectivity in the open state. Here, we achieve higher-resolution structures of the open and closed states and employ molecular dynamics simulations to analyze the conducting properties of the putative open state, demonstrating that it is permeable to K+ and, to a lesser degree, also Na+. Both cations must dehydrate significantly to penetrate the narrow hydrophobic constriction, but ion flow is assisted by a favorable electrostatic field generated by the protein that spans the length of the pore. The balance of these opposing energetic factors explains why permeation is feasible, and why TMEM175 is selective for K+ over Na+, despite the absence of the canonical selectivity filter. Accordingly, mutagenesis experiments reveal an exquisite sensitivity of the channel to perturbations that mitigate the constriction. Together, these data reveal a novel mechanism for selective permeation of ions by TMEM175 that is unlike that of other K+ channels.
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Affiliation(s)
- SeCheol Oh
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Fabrizio Marinelli
- Theoretical Molecular Biophysics Section, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Wenchang Zhou
- Theoretical Molecular Biophysics Section, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Jooyeon Lee
- Department of Chemistry, Chungbuk National University, Cheongju-si, Republic of Korea
| | - Ho Jeong Choi
- Department of Chemistry, Chungbuk National University, Cheongju-si, Republic of Korea
| | - Min Kim
- Department of Chemistry, Chungbuk National University, Cheongju-si, Republic of Korea
| | - José D Faraldo-Gómez
- Theoretical Molecular Biophysics Section, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Richard K Hite
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
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Mercado-Montijo J, Anstine DM, Rukmani SJ, Colina CM, Andrew JS. PEGDA hydrogel structure from semi-dilute concentrations: insights from experiments and molecular simulations. Soft Matter 2022; 18:3565-3574. [PMID: 35466967 DOI: 10.1039/d1sm01708j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The efficacy of hydrogel materials used in biomedical applications is dependent on polymer network topology and the structure of water-laden pore space. Hydrogel microstructure can be tuned by adjusting synthesis parameters such as macromer molar mass and concentration. Moreover, hydrogels beyond dilute conditions are needed to produce mechanically robust and dense networks for tissue engineering and/or drug delivery systems. Thus, this study utilizes a combined experimental and molecular simulation approach to characterize structural features for 4.8 and 10 kDa poly (ethylene glycol) diacrylate (PEGDA) hydrogels formed from a range of semi-dilute solution concentrations. The connection between chain-chain interactions in polymer solutions, hydrogel structure, and equilibrium swelling behavior is presented. Bulk rheology analysis revealed an entanglement concentration for PEGDA pre-gel solutions around 28 wt% for both macromers studied. A similar transition in swelling behavior was revealed around the same concentration where hydrogel capacity to retain water was drastically reduced. To understand this transition, the hydrogel structure was characterized using the swollen polymer network hypothesis and compared to pore size distributions from molecular dynamics simulations. We find in both approaches a structural transition concentration at the hydrogel swelling inflection point that is comparable to the entanglement concentration. Calculated mesh sizes from theory are compared with computationally determined average maximum pore diameters; mesh sizes from theory yielded greater feature sizes across all concentrations considered. Molecular simulations are further used to assess pore dynamics, which are shown to vary in distribution shape and number of modes compared to the time-averaged hydrogel pore features. Altogether, this work provides insights into hydrogel network features and their dynamic behavior at physiological conditions (37 °C) as a basis for hydrogel design beyond dilute conditions for biomedical applications.
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Affiliation(s)
- Jomary Mercado-Montijo
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.
| | - Dylan M Anstine
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.
- George and Josephine Butler Polymer Research Laboratory, University of Florida, Gainesville, Florida 32611, USA
| | - Shalini J Rukmani
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.
- George and Josephine Butler Polymer Research Laboratory, University of Florida, Gainesville, Florida 32611, USA
| | - Coray M Colina
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.
- George and Josephine Butler Polymer Research Laboratory, University of Florida, Gainesville, Florida 32611, USA
- Department of Chemistry, University of Florida, Gainesville, Florida 32611, USA
| | - Jennifer S Andrew
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.
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