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Sam S, Sung S, Kim D. Sensitive Detection of Biomolecular Adsorption by a Low-Density Surfactant Layer Using Sum-Frequency Vibrational Spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:17412-17419. [PMID: 38050679 DOI: 10.1021/acs.langmuir.3c02546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2023]
Abstract
Small molecules or proteins interact with a biomembrane in various ways for molecular recognition, structure stabilization, and transmembrane signaling. In this study, 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP), having a choline group, was used to investigate this interaction by using sum-frequency vibrational spectroscopy. The sum-frequency spectrum characteristic of a neat monolayer changed to that of a bare air/water interface at a larger molecular area of the DPTAP molecules due to local laser heating. Upon introduction of the aromatic molecules in the subphase at around 120 Å2 per molecule, the sum-frequency signal suddenly reappeared due to molecular adhesion, and this was utilized to probe the adsorption of the aromatic ring molecules in the water subphase to the choline headgroup of the DPTAP by cation-π interaction. The onset concentrations of this sum-frequency signal change allowed a comparison of the relative interaction strengths between different aromatic molecules. A zwitterionic surfactant molecule (DPPC) was found to interact weakly compared to the cationic DPTAP molecule.
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Affiliation(s)
- Sokhuoy Sam
- Department of Physics, Sogang University, 35, Baekbeom-ro, Mapo-gu, Seoul, 04107, Korea
| | - Siheon Sung
- Department of Physics, Sogang University, 35, Baekbeom-ro, Mapo-gu, Seoul, 04107, Korea
| | - Doseok Kim
- Department of Physics, Sogang University, 35, Baekbeom-ro, Mapo-gu, Seoul, 04107, Korea
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2
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Anderson DM, Jayanthi LP, Gosavi S, Meiering EM. Engineering the kinetic stability of a β-trefoil protein by tuning its topological complexity. Front Mol Biosci 2023; 10:1021733. [PMID: 36845544 PMCID: PMC9945329 DOI: 10.3389/fmolb.2023.1021733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 01/02/2023] [Indexed: 02/11/2023] Open
Abstract
Kinetic stability, defined as the rate of protein unfolding, is central to determining the functional lifetime of proteins, both in nature and in wide-ranging medical and biotechnological applications. Further, high kinetic stability is generally correlated with high resistance against chemical and thermal denaturation, as well as proteolytic degradation. Despite its significance, specific mechanisms governing kinetic stability remain largely unknown, and few studies address the rational design of kinetic stability. Here, we describe a method for designing protein kinetic stability that uses protein long-range order, absolute contact order, and simulated free energy barriers of unfolding to quantitatively analyze and predict unfolding kinetics. We analyze two β-trefoil proteins: hisactophilin, a quasi-three-fold symmetric natural protein with moderate stability, and ThreeFoil, a designed three-fold symmetric protein with extremely high kinetic stability. The quantitative analysis identifies marked differences in long-range interactions across the protein hydrophobic cores that partially account for the differences in kinetic stability. Swapping the core interactions of ThreeFoil into hisactophilin increases kinetic stability with close agreement between predicted and experimentally measured unfolding rates. These results demonstrate the predictive power of readily applied measures of protein topology for altering kinetic stability and recommend core engineering as a tractable target for rationally designing kinetic stability that may be widely applicable.
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Affiliation(s)
| | - Lakshmi P. Jayanthi
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Shachi Gosavi
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Elizabeth M. Meiering
- Department of Chemistry, University of Waterloo, Waterloo, ON, Canada,*Correspondence: Elizabeth M. Meiering,
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3
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MacKenzie DWS, Schaefer A, Steckner J, Leo CA, Naser D, Artikis E, Broom A, Ko T, Shah P, Ney MQ, Tran E, Smith MTJ, Fuglestad B, Wand AJ, Brooks CL, Meiering EM. A fine balance of hydrophobic-electrostatic communication pathways in a pH-switching protein. Proc Natl Acad Sci U S A 2022; 119:e2119686119. [PMID: 35737838 PMCID: PMC9245636 DOI: 10.1073/pnas.2119686119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 03/29/2022] [Indexed: 12/24/2022] Open
Abstract
Allostery is the phenomenon of coupling between distal binding sites in a protein. Such coupling is at the crux of protein function and regulation in a myriad of scenarios, yet determining the molecular mechanisms of coupling networks in proteins remains a major challenge. Here, we report mechanisms governing pH-dependent myristoyl switching in monomeric hisactophilin, whereby the myristoyl moves between a sequestered state, i.e., buried within the core of the protein, to an accessible state, in which the myristoyl has increased accessibility for membrane binding. Measurements of the pH and temperature dependence of amide chemical shifts reveal protein local structural stability and conformational heterogeneity that accompany switching. An analysis of these measurements using a thermodynamic cycle framework shows that myristoyl-proton coupling at the single-residue level exists in a fine balance and extends throughout the protein. Strikingly, small changes in the stereochemistry or size of core and surface hydrophobic residues by point mutations readily break, restore, or tune myristoyl switch energetics. Synthesizing the experimental results with those of molecular dynamics simulations illuminates atomistic details of coupling throughout the protein, featuring a large network of hydrophobic interactions that work in concert with key electrostatic interactions. The simulations were critical for discerning which of the many ionizable residues in hisactophilin are important for switching and identifying the contributions of nonnative interactions in switching. The strategy of using temperature-dependent NMR presented here offers a powerful, widely applicable way to elucidate the molecular mechanisms of allostery in proteins at high resolution.
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Affiliation(s)
| | - Anna Schaefer
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Julia Steckner
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Christopher A. Leo
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Dalia Naser
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Efrosini Artikis
- Department of Chemistry and Biophysics, University of Michigan, Ann Arbor, MI 48109
| | - Aron Broom
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Travis Ko
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Purnank Shah
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Mikaela Q. Ney
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Elisa Tran
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Martin T. J. Smith
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Brian Fuglestad
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - A. Joshua Wand
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Charles L. Brooks
- Department of Chemistry and Biophysics, University of Michigan, Ann Arbor, MI 48109
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Kumawat A, Chakrabarty S. Protonation-Induced Dynamic Allostery in PDZ Domain: Evidence of Perturbation-Independent Universal Response Network. J Phys Chem Lett 2020; 11:9026-9031. [PMID: 33043672 DOI: 10.1021/acs.jpclett.0c02885] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Dynamic allostery is a relatively new paradigm where certain external perturbations may lead to modulation of conformational dynamics at a distant part of a protein without significant changes in the overall structure. While most well-characterized examples of dynamic allostery involve binding with other entities like small molecules, peptides, or nucleic acids, in this work we demonstrate that chemical modifications like protonation may lead to significant dynamical allosteric response in a PDZ domain protein. Tuning the protonation states of two histidine residues (H317 and H372), we identify the allosteric pathways responsible for the dynamic response. Interestingly, the same set of residues that constitute the allosteric response network upon ligand binding seem to be responsible for protonation-induced dynamic allostery. Thus, we propose the existence of an inherent universal response network in signaling proteins, where the same set of residues can respond to varying types of external perturbations in terms of rearrangement of hydrogen-bonded network and redistribution of electrostatic interaction energies.
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Affiliation(s)
- Amit Kumawat
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
| | - Suman Chakrabarty
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata 700106, India
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Anwer W, Ratto Velasquez A, Tsoukanova V. Acylcarnitines at the Membrane Surface: Insertion Parameters for a Mitochondrial Leaflet Model. Biophys J 2020; 118:1032-1043. [PMID: 32027823 DOI: 10.1016/j.bpj.2020.01.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/11/2019] [Accepted: 01/14/2020] [Indexed: 12/28/2022] Open
Abstract
Excessive accumulation of acylcarnitines (ACs), often caused by metabolic disorders, has been associated with obesity, arrhythmias, cardiac ischemia, insulin resistance, etc. Mechanisms whereby elevated ACs might contribute to pathophysiological effects remain largely unexplored. We have aimed to gain insight into AC interactions with the mitochondrial inner membrane. To model its outer leaflet, Langmuir monolayers and cushioned supported bilayers were employed. Their interactions with ACs were monitored with epifluorescence microscopy, which revealed a local leaflet expansion upon exposure to elevated concentrations of a long-chain AC, plausibly caused by its insertion. To assess the AC insertion parameters, constant-pressure insertion assays were performed. A value of 21 ± 3 Å2 was obtained for the AC insertion area, which is roughly the same as the cross-sectional area of an acyl chain. By contrast, the carnitine moiety was found to require an area of 37 ± 3 Å2. The AC insertion has thus been concluded to involve solely the AC acyl chain. This mode of insertion implies that the carnitine moiety, with its nontitratable positive charge, is left dangling at the membrane surface, which is likely to alter the surface electrostatics of the outer leaflet. The extrapolation of these findings has enabled us to hypothesize that, by altering the morphology and surface electrostatics of the outer leaflet, the insertion of ACs, in particular their long-chain counterparts, may trigger a nonspecific activation of signaling pathways in the inner mitochondrial membrane, thereby modulating its function and potentially leading to pathophysiological responses.
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Affiliation(s)
- Wajih Anwer
- Department of Chemistry, York University, Toronto, Ontario, Canada
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6
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Blanco PM, Madurga S, Narambuena CF, Mas F, Garcés JL. Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes. Polymers (Basel) 2019; 11:polym11121962. [PMID: 31795443 PMCID: PMC6960815 DOI: 10.3390/polym11121962] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 11/21/2019] [Accepted: 11/25/2019] [Indexed: 01/29/2023] Open
Abstract
This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte that is, proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included. This model can be regarded as a kind of “minimal” in the sense that it contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both, with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 at low pH-values (Pincus regime) is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to the changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.
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Affiliation(s)
- Pablo M. Blanco
- Physical Chemistry Unit, Materials Science and Physical Chemistry Department & Research Institute of Theoretical and Computational Chemistry (IQTCUB) of Barcelona University (UB), 08028 Barcelona, Catalonia, Spain;
- Correspondence: (P.M.B.); (F.M.)
| | - Sergio Madurga
- Physical Chemistry Unit, Materials Science and Physical Chemistry Department & Research Institute of Theoretical and Computational Chemistry (IQTCUB) of Barcelona University (UB), 08028 Barcelona, Catalonia, Spain;
| | - Claudio F. Narambuena
- Facultad Regional San Rafael, Universidad Tecnológica Nacional & Instituto de Física Aplicada (INFAP), Universidad Nacional de San Luis-CONICET, 5600 San Rafael, Argentina;
| | - Francesc Mas
- Physical Chemistry Unit, Materials Science and Physical Chemistry Department & Research Institute of Theoretical and Computational Chemistry (IQTCUB) of Barcelona University (UB), 08028 Barcelona, Catalonia, Spain;
- Correspondence: (P.M.B.); (F.M.)
| | - Josep L. Garcés
- Chemistry Department, Technical School of Agricultural Engineering & AGROTECNIO of Lleida University (UdL), 25003 Lleida, Catalonia, Spain;
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7
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Zhang G, Wang H, Zhu K, Yang Y, Li J, Jiang H, Liu Z. Investigation of candidate molecular biomarkers for expression profile analysis of the Gene expression omnibus (GEO) in acute lymphocytic leukemia (ALL). Biomed Pharmacother 2019; 120:109530. [PMID: 31606621 DOI: 10.1016/j.biopha.2019.109530] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 09/17/2019] [Accepted: 10/02/2019] [Indexed: 01/17/2023] Open
Abstract
Much progress has been made in understanding the mechanism of acute lymphocytic leukemia (ALL). However, for adult ALL, there is still a lack of an effective treatment. In the present study, we first used the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) between ALL cell lines and Hodgkin and non-Hodgkin cell lines. Then, the GEO database was also used to detect the DEGs in acute lymphoblastic leukemia (Reh) cells transfected with a normal control or a constitutively active variant of the IkB kinase β. Finally, we found that three key DEGs (CCL5, FSCN1, and HS3ST1) are involved in proliferation and apoptosis according to Gene Ontology (GO) and Kyoto Encyclopedia of Genes Genomes (KEGG) pathway analyses. Finally, we determined that all three target genes that participate in proliferation and apoptosis are regulated via the NF-kB signaling pathway.
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Affiliation(s)
- Guojun Zhang
- Department of Hematology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Hongtao Wang
- Department of Hematology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Ke Zhu
- Department of Hematology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Ying Yang
- Department of Hematology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Jia Li
- Department of Hematology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Huinan Jiang
- Department of Hematology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Zhuogang Liu
- Department of Hematology, Shengjing Hospital of China Medical University, Shenyang, China.
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8
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Cornell RB, Taneva SG, Dennis MK, Tse R, Dhillon RK, Lee J. Disease-linked mutations in the phosphatidylcholine regulatory enzyme CCTα impair enzymatic activity and fold stability. J Biol Chem 2018; 294:1490-1501. [PMID: 30559292 DOI: 10.1074/jbc.ra118.006457] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 12/05/2018] [Indexed: 11/06/2022] Open
Abstract
CTP:phosphocholine cytidylyltransferase (CCT) is the key regulatory enzyme in phosphatidylcholine (PC) synthesis and is activated by binding to PC-deficient membranes. Mutations in the gene encoding CCTα (PCYT1A) cause three distinct pathologies in humans: lipodystrophy, spondylometaphyseal dysplasia with cone-rod dystrophy (SMD-CRD), and isolated retinal dystrophy. Previous analyses showed that for some disease-linked PCYT1A variants steady state levels of CCTα and PC synthesis were reduced in patient fibroblasts, but other variants impaired PC synthesis with little effect on CCT levels. To explore the impact on CCT stability and function we expressed WT and mutant CCTs in COS-1 cells, which have very low endogenous CCT. Over-expression of two missense variants in the catalytic domain (V142M and P150A) generated aggregated enzymes that could not be refolded after solubilization by denaturation. Other mutations in the catalytic core that generated CCTs with reduced solubility could be purified. Five variants destabilized the catalytic domain-fold as assessed by lower transition temperatures for unfolding, and three of these manifested defects in substrate Km values. A mutation (R223S) in a signal-transducing linker between the catalytic and membrane-binding domains also impaired enzyme kinetics. E280del, a single amino acid deletion in the autoinhibitory helix increased the constitutive (lipid-independent) enzyme activity ∼4-fold. This helix also participates in membrane binding, and surprisingly E280del enhanced the enzyme's response to anionic lipid vesicles ∼4-fold. These in vitro analyses on purified mutant CCTs will complement future measurements of their impact on PC synthesis in cultured cells and in tissues with a stringent requirement for CCTα.
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Affiliation(s)
- Rosemary B Cornell
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada; Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada.
| | - Svetla G Taneva
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada
| | - Melissa K Dennis
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada
| | - Ronnie Tse
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada
| | - Randeep K Dhillon
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada
| | - Jaeyong Lee
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada
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9
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Adamczewski P, Tsoukanova V. Phenylalanine intercalation parameters for liquid-disordered phase domains - a membrane model study. BMC BIOPHYSICS 2018; 11:6. [PMID: 30473783 PMCID: PMC6237005 DOI: 10.1186/s13628-018-0047-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 10/31/2018] [Indexed: 12/17/2022]
Abstract
BACKGROUND Propensity of phenylalanine (Phe) for nonpolar environments drives its intercalation into phospholipid membranes, which has been implicated in metabolic and neurological disorders. The knowledge of Phe intercalation parameters can be instrumental in understanding various membrane processes triggered by interactions with Phe, in particular the early events leading to the formation of nucleation/docking sites for the self-assembly of Phe amyloid fibrils at the membrane surface. RESULTS In this study, we used monolayers of phosphatidylethanolamine (DPPE) and phosphatidylcholine (DPPC) to mimic the membrane outer leaflet. Its initial interaction with Phe was modeled by injecting Phe into the aqueous phase underneath the monolayer. Constant pressure insertion assays augmented with epifluorescence microscopy imaging were used to monitor Phe intercalation. Our primary goal was to determine the Phe intercalation area, A Phe. Two values were obtained for A Phe, 33 ± 2 and 48 ± 3 Å2. CONCLUSIONS Phe appeared to discriminate between DPPE and DPPC packing, and use two modes of intercalation. The area of A Phe 33 ± 2 Å2 is consistent with a Phe monomer intercalating into membrane by inserting the phenyl ring nearly normal to the membrane surface. This mode has been found to operate in DPPE membranes. For DPPC membranes however, the value of A Phe = 48 ± 3 Å2 suggests that, from saline, Phe tends to intercalate as a larger species plausibly dragging along a counterion, Na+, in a Na+(Phe) complex.
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Khan MV, Rabbani G, Ahmad E, Khan RH. Fluoroalcohols-induced modulation and amyloid formation in conalbumin. Int J Biol Macromol 2014; 70:606-14. [DOI: 10.1016/j.ijbiomac.2014.07.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/27/2014] [Accepted: 07/09/2014] [Indexed: 10/25/2022]
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Olety B, Ono A. Roles played by acidic lipids in HIV-1 Gag membrane binding. Virus Res 2014; 193:108-15. [PMID: 24998886 DOI: 10.1016/j.virusres.2014.06.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2014] [Revised: 06/18/2014] [Accepted: 06/23/2014] [Indexed: 10/25/2022]
Abstract
The MA domain mediates plasma membrane (PM) targeting of HIV-1 Gag, leading to particle assembly at the PM. The interaction between MA and acidic phospholipids, in addition to N-terminal myristoyl moiety, promotes Gag binding to lipid membranes. Among acidic phospholipids, PI(4,5)P2, a PM-specific phosphoinositide, is essential for proper HIV-1 Gag localization to the PM and efficient virus particle production. Recent studies further revealed that MA-bound RNA negatively regulates HIV-1 Gag membrane binding and that PI(4,5)P2 is necessary to overcome this RNA-imposed block. In this review, we will summarize the current understanding of Gag-membrane interactions and discuss potential roles played by acidic phospholipids.
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Affiliation(s)
- Balaji Olety
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Akira Ono
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, United States.
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12
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Nam JS, Chakraborty C, Sharma AR, Her Y, Bae KJ, Sharma G, Doss GP, Lee SS, Hong MS, Song DK. Effect of Wnt3a on keratinocytes utilizing in vitro and bioinformatics analysis. Int J Mol Sci 2014; 15:5472-95. [PMID: 24686518 PMCID: PMC4013576 DOI: 10.3390/ijms15045472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Revised: 03/07/2014] [Accepted: 03/12/2014] [Indexed: 11/25/2022] Open
Abstract
Wingless-type (Wnt) signaling proteins participate in various cell developmental processes. A suppressive role of Wnt5a on keratinocyte growth has already been observed. However, the role of other Wnt proteins in proliferation and differentiation of keratinocytes remains unknown. Here, we investigated the effects of the Wnt ligand, Wnt3a, on proliferation and differentiation of keratinocytes. Keratinocytes from normal human skin were cultured and treated with recombinant Wnt3a alone or in combination with the inflammatory cytokine, tumor necrosis factor α (TNFα). Furthermore, using bioinformatics, we analyzed the biochemical parameters, molecular evolution, and protein–protein interaction network for the Wnt family. Application of recombinant Wnt3a showed an anti-proliferative effect on keratinocytes in a dose-dependent manner. After treatment with TNFα, Wnt3a still demonstrated an anti-proliferative effect on human keratinocytes. Exogenous treatment of Wnt3a was unable to alter mRNA expression of differentiation markers of keratinocytes, whereas an altered expression was observed in TNFα-stimulated keratinocytes. In silico phylogenetic, biochemical, and protein–protein interaction analysis showed several close relationships among the family members of the Wnt family. Moreover, a close phylogenetic and biochemical similarity was observed between Wnt3a and Wnt5a. Finally, we proposed a hypothetical mechanism to illustrate how the Wnt3a protein may inhibit the process of proliferation in keratinocytes, which would be useful for future researchers.
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Affiliation(s)
- Ju-Suk Nam
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
| | - Chiranjib Chakraborty
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
| | - Ashish Ranjan Sharma
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
| | - Young Her
- Department of Dermatology, School of Medicine, Kangwon National University Hospital, Chuncheon 200722, Korea.
| | - Kee-Jeong Bae
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
| | - Garima Sharma
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
| | - George Priya Doss
- Medical Biotechnology Division, School of Biosciences and Technology, VIT University, Vellore 632014, Tamil Nadu, India.
| | - Sang-Soo Lee
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
| | - Myung-Sun Hong
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
| | - Dong-Keun Song
- Institute for Skeletal Aging & Orthopedic Surgery, Hallym University-Chuncheon Sacred Heart Hospital, Chuncheon 200704, Korea.
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13
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Gasbarri C, Angelini G. Spectroscopic investigation of fluorinated phenols as pH-sensitive probes in mixed liposomal systems. RSC Adv 2014. [DOI: 10.1039/c4ra01507j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The pKa values of three fluorinated phenols, 2,4,6-trifluorophenol (3FP), 2,3,5,6-tetrafluorophenol (4FP) and 2,3,4,5,6-pentafluorophenol (5FP) have been measured by using UV-vis and 19F-NMR spectroscopy at 25 °C in water and in the presence of pure POPC, pure DDAB and mixed POPC–DDAB liposomes.
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Affiliation(s)
- Carla Gasbarri
- Dipartimento di Farmacia
- Università G. d'Annunzio di Chieti-Pescara
- 66100 Chieti, Italy
| | - Guido Angelini
- Dipartimento di Farmacia
- Università G. d'Annunzio di Chieti-Pescara
- 66100 Chieti, Italy
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14
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Heo SM, Ruhl S, Scannapieco FA. Implications of salivary protein binding to commensal and pathogenic bacteria. J Oral Biosci 2013; 55:169-174. [PMID: 24707190 PMCID: PMC3974197 DOI: 10.1016/j.job.2013.06.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
An important function of salivary proteins is to interact with microorganisms that enter the oral cavity. For some microbes, these interactions promote microbial colonization. For others, these interactions are deleterious and result in the elimination of the microbe from the mouth, This paper reviews recent studies of the interaction of salivary proteins with two model bacteria; the commensal species Streptococcus gordonii, and the facultative pathogen Staphylococcus aureus. These organisms selectively interact with a variety of salivary proteins to influence important functions such as bacterial adhesion to surfaces, evasion of host defense, bacterial nutrition and metabolism and gene expression.
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Affiliation(s)
- Seok-Mo Heo
- Department of Periodontology, School of Dentistry, Chonbuk National University, Jeonju, Republic of Korea
| | | | - Frank A. Scannapieco
- Corresponding author: Department of Oral Biology, School of Dental Medicine, University at Buffalo, The State University of New York, Foster Hall, Buffalo, New York 14214,
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Abstract
AbstractProteins and other biomolecules contain acidic and basic titratable groups that give rise to intricate charge distributions and control electrostatic interactions. ‘Charge regulation’ concerns how the proton equilibria of these sites are perturbed when approached by alien molecular matter such as other proteins, surfaces and membranes, DNA, polyelectrolytes etc. Importantly, this perturbation generates a charge response that leads to attractive intermolecular interactions that can be conveniently described by a single molecular property – the charge capacitance. The capacitance quantifies molecular charge fluctuations, i.e. it is the variance of the mean charge and is an intrinsic property on par with the net charge and the dipole moment. It directly enters the free energy expression for intermolecular interactions and can be obtained experimentally from the derivative of the titration curve or theoretically from simulations. In this review, we focus on the capacitance concept as a predictive parameter for charge regulation and demonstrate how it can be used to estimate the interaction of a protein with other proteins, polyelectrolytes, membranes as well as with ligands.
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16
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Liu DC, Jow GM, Chuang CC, Peng YJ, Hsu PH, Tang CY. Densin-180 is Not a Transmembrane Protein. Cell Biochem Biophys 2013; 67:773-83. [PMID: 23516094 DOI: 10.1007/s12013-013-9570-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Dai-Chi Liu
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
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17
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Schönichen A, Webb BA, Jacobson MP, Barber DL. Considering protonation as a posttranslational modification regulating protein structure and function. Annu Rev Biophys 2013; 42:289-314. [PMID: 23451893 DOI: 10.1146/annurev-biophys-050511-102349] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Posttranslational modification is an evolutionarily conserved mechanism for regulating protein activity, binding affinity, and stability. Compared with established posttranslational modifications such as phosphorylation or ubiquitination, posttranslational modification by protons within physiological pH ranges is a less recognized mechanism for regulating protein function. By changing the charge of amino acid side chains, posttranslational modification by protons can drive dynamic changes in protein conformation and function. Addition and removal of a proton is rapid and reversible and, in contrast to most other posttranslational modifications, does not require an enzyme. Signaling specificity is achieved by only a minority of sites in proteins titrating within the physiological pH range. Here, we examine the structural mechanisms and functional consequences of proton posttranslational modification of pH-sensing proteins regulating different cellular processes.
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Affiliation(s)
- André Schönichen
- Department of Cell and Tissue Biology, University of California, San Francisco, USA
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18
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Trulsson M, Jönsson B, Labbez C. On the origin of the halo stabilization. Phys Chem Chem Phys 2013; 15:541-5. [DOI: 10.1039/c2cp42404e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Preininger AM, Kaya AI, Gilbert JA, Busenlehner LS, Armstrong RN, Hamm HE. Myristoylation exerts direct and allosteric effects on Gα conformation and dynamics in solution. Biochemistry 2012; 51:1911-24. [PMID: 22329346 DOI: 10.1021/bi201472c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Coupling of heterotrimeric G proteins to activated G protein-coupled receptors results in nucleotide exchange on the Gα subunit, which in turn decreases its affinity for both Gβγ and activated receptors. N-Terminal myristoylation of Gα subunits aids in membrane localization of inactive G proteins. Despite the presence of the covalently attached myristoyl group, Gα proteins are highly soluble after GTP binding. This study investigated factors facilitating the solubility of the activated, myristoylated protein. In doing so, we also identified myristoylation-dependent differences in regions of Gα known to play important roles in interactions with receptors, effectors, and nucleotide binding. Amide hydrogen-deuterium exchange and site-directed fluorescence of activated proteins revealed a solvent-protected amino terminus that was enhanced by myristoylation. Furthermore, fluorescence quenching confirmed that the myristoylated amino terminus is in proximity to the Switch II region in the activated protein. Myristoylation also stabilized the interaction between the guanine ring and the base of the α5 helix that contacts the bound nucleotide. The allosteric effects of myristoylation on protein structure, function, and localization indicate that the myristoylated amino terminus of Gα(i) functions as a myristoyl switch, with implications for myristoylation in the stabilization of nucleotide binding and in the spatial regulation of G protein signaling.
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Affiliation(s)
- Anita M Preininger
- Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States
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Wang WY, Zhang L, Xing S, Ma Z, Liu J, Gu H, Qin G, Qu LJ. Arabidopsis AtVPS15 plays essential roles in pollen germination possibly by interacting with AtVPS34. J Genet Genomics 2012; 39:81-92. [PMID: 22361507 DOI: 10.1016/j.jgg.2012.01.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 01/04/2012] [Accepted: 01/05/2012] [Indexed: 10/14/2022]
Abstract
VPS15 protein is a component of the phosphatidylinositol 3-kinase complex which plays a pivotal role in the development of yeast and mammalian cells. The knowledge about the function of its homologue in plants remains limited. Here we report that AtVPS15, a homologue of yeast VPS15p in Arabidopsis, plays an essential role in pollen germination. Homozygous T-DNA insertion mutants of AtVPS15 could not be obtained from the progenies of self-pollinated heterozygous mutants. Reciprocal crosses between atvps15 mutants and wild-type Arabidopsis revealed that the T-DNA insertion was not able to be transmitted by male gametophytes. DAPI staining, Alexander's stain and scanning electron microscopic analysis showed that atvps15 heterozygous plants produced pollen grains that were morphologically indistinguishable from wild-type pollen, whereas in vitro germination experiments revealed that germination of the pollen grains was defective. GUS staining analysis of transgenic plants expressing the GUS reporter gene driven by the AtVPS15 promoter showed that AtVPS15 was mainly expressed in pollen grains. Finally, DUALmembrane yeast two-hybrid analysis demonstrated that AtVPS15 might interact directly with AtVPS34. These results suggest that AtVPS15 is very important for pollen germination, possibly through modulation of the activity of PI3-kinase.
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Affiliation(s)
- Wei-Ying Wang
- State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
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pH-Induced Molten Globule State of Rhizopus niveus Lipase is More Resistant Against Thermal and Chemical Denaturation Than Its Native State. Cell Biochem Biophys 2012; 62:487-99. [DOI: 10.1007/s12013-011-9335-9] [Citation(s) in RCA: 178] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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22
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pH-Dependent Conformational Transitions in Conalbumin (Ovotransferrin), a Metalloproteinase from Hen Egg White. Cell Biochem Biophys 2011; 61:551-60. [DOI: 10.1007/s12013-011-9237-x] [Citation(s) in RCA: 147] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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23
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Hashimoto Y, Kim DJ, Adams JC. The roles of fascins in health and disease. J Pathol 2011; 224:289-300. [DOI: 10.1002/path.2894] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 03/02/2011] [Accepted: 03/04/2011] [Indexed: 02/06/2023]
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24
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Stakkestad Ø, Larsen ACV, Kvissel AK, Eikvar S, Ørstavik S, Skålhegg BS. Protein kinase A type I activates a CRE-element more efficiently than protein kinase A type II regardless of C subunit isoform. BMC BIOCHEMISTRY 2011; 12:7. [PMID: 21303506 PMCID: PMC3060122 DOI: 10.1186/1471-2091-12-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 02/08/2011] [Indexed: 12/16/2022]
Abstract
Background Protein kinase A type I (PKAI) and PKAII are expressed in most of the eukaryotic cells examined. PKA is a major receptor for cAMP and specificity is achieved partly through tissue-dependent expression and subcellular localization of subunits with different biochemical properties. In addition posttranslational modifications help fine tune PKA activity, distribution and interaction in the cell. In spite of this the functional significance of two forms of PKA in one cell has not been fully determined. Here we have tested the ability of PKAI and PKAII formed by expression of the regulatory (R) subunits RIα or RIIα in conjunction with Cα1 or Cβ2 to activate a co-transfected luciferace reporter gene, controlled by the cyclic AMP responsive element-binding protein (CREB) in vivo. Results We show that PKAI when expressed at equal levels as PKAII was significantly (p < 0.01) more efficient in inducing Cre-luciferace activity at saturating concentrations of cAMP. This result was obtained regardless of catalytic subunit identity. Conclusion We suggest that differential effects of PKAI and PKAII in inducing Cre-luciferace activity depend on R and not C subunit identity.
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Affiliation(s)
- Øystein Stakkestad
- Department of Nutrition, Institute for Basic Medical Sciences, University of Oslo, Sognsvannsveien 9, P,O, Box 1046 Blindern, N- 0316 OSLO, Norway
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Energetics and mechanisms of folding and flipping the myristoyl switch in the {beta}-trefoil protein, hisactophilin. Proc Natl Acad Sci U S A 2010; 107:20952-7. [PMID: 21097705 DOI: 10.1073/pnas.1008026107] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Myristoylation, the covalent linkage of a saturated, C(14) fatty acyl chain to the N-terminal glycine in a protein, plays a vital role in reversible membrane binding and signaling by the modified proteins. Currently, little is known about the effects of myristoylation on protein folding and stability, or about the energetics and molecular mechanisms of switching involving states with sequestered versus accessible myristoyl group. Our analysis of these effects in hisactophilin, a histidine-rich protein that binds cell membranes and actin in a pH-dependent manner, shows that myristoylation significantly increases hisactophilin stability, while also markedly increasing global protein folding and unfolding rates. The switching between sequestered and accessible states is pH dependent, with an apparent pK(switch) of 6.95, and an apparent free energy change of 2.0 kcal·mol(-1). The myristoyl switch is linked to the reversible uptake of ∼1.5 protons, likely by histidine residues. This pH dependence of switching appears to be the physical basis of the sensitive, pH-dependent regulation of membrane binding observed in vivo. We conclude that an increase in protein stability upon modification and burial of the attached group is likely to occur in numerous proteins modified with fatty acyl or other hydrophobic groups, and that the biophysical effects of such modification are likely to play an important role in their functional switches. In addition, the increased global dynamics caused by myristoylation of hisactophilin reveals a general mechanism whereby hydrophobic moieties can make nonnative interactions or relieve strain in transition states, thereby increasing the rates of interconversion between different states.
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26
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Smith MTJ, MacKenzie DWS, Meiering EM. Dissecting the molecular determinants of ligand-binding-induced macromolecular switching using thermodynamic cycles. Protein Eng Des Sel 2010; 24:213-7. [DOI: 10.1093/protein/gzq099] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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27
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Beck A, Li-Blatter X, Seelig A, Seelig J. On the interaction of ionic detergents with lipid membranes. Thermodynamic comparison of n-alkyl-+N(CH₃)₃ and n-alkyl-SO₄⁻. J Phys Chem B 2010; 114:15862-71. [PMID: 21067191 DOI: 10.1021/jp107088d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ionic detergents find widespread commercial applications as disinfectants, fungicides, or excipients in drug formulations and cosmetics. One mode of action is their ease of insertion into biological membranes. Very little quantitative information on this membrane-binding process is available to date. Using isothermal titration calorimetry (ITC) and dynamic light scattering (DLS), we have made a systematic comparison of the binding of cationic and anionic detergents to neutral and negatively charged lipid membranes. The detergents investigated were n-alkyl chains carrying either the trimethylammonium chloride (-(+)N(CH₃)₃Cl⁻) or the sodium sulfate (-SO₄⁻Na(+)) headgroup with chain lengths of n = 10-16. The titration of lipid vesicles into detergent solutions provided the binding enthalpy and the binding isotherm in a model-independent manner. At 25 °C the membrane binding enthalpies, ΔH(mem)(0), were small (-0.4 to -4.2 kcal/mol) and showed little correlation with the length of the alkyl chains. The ITC binding isotherms were analyzed in terms of a surface partition model. To this purpose, the surface concentration, cM, of detergent immediately above the plane of binding was calculated with the Gouy-Chapman theory. The surface concentration corrects for electrostatic attraction or repulsion and can be larger or smaller than the bulk detergent concentration, c(eq), at equilibrium. The analysis provides the chemical or hydrophobic binding constant, K(D)(0), of the detergent and the corresponding free energy. The free energies of binding, ΔG(mem)(0), vary between -4 and -10 kcal/mol. They show a linear dependence on the chain length, which can be used to separate the contributions of the polar group and the hydrocarbon tail in membrane binding. The neutral maltose and the cationic (+)N(CH₃)₃ headgroup show steric repulsion energies of about 2.5 kcal/mol counteracting the hydrophobic binding of the alkyl tail, whereas the anionic SO₄⁻ headgroup makes almost no contribution to membrane binding. The chemical nature of the headgroup influences the packing density of the hydrocarbon chains in the lipid bilayer with (+)N(CH₃)₃ eliciting the weakest chain-chain interaction. The minimum repulsive interaction of the SO₄⁻ polar group makes the sodium n-alkyl-sulfates much stronger detergents than the nonionic or cationic counterparts, the binding constants, K(D)(0), being 10-50 times larger than those of the corresponding n-alkyl-trimethylammonium chlorides. The membrane insertion was further compared with micelle formation of the same detergent. A cooperative aggregation model which includes all possible aggregation states is proposed to analyze micelle formation. The partition function can be defined in closed form, and it is straightforward to predict the thermodynamic properties of the micellar system. When aggregated in micelles, the detergent polar groups are in direct interaction and are not separated by lipid molecules. Under these conditions the SO₄⁻ group exhibits a strong electrostatic repulsive effect of 3.2 kcal/mol, while the contributions of the maltose and (+)N(CH₃)₃ headgroups are very similar to those in the lipid bilayer.
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Affiliation(s)
- Andreas Beck
- Biozentrum, University of Basel, Division of Biophysical Chemistry, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
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28
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Staes E, Absil PA, Lins L, Brasseur R, Deleu M, Lecouturier N, Fievez V, Rieux AD, Mingeot-Leclercq MP, Raussens V, Préat V. Acylated and unacylated ghrelin binding to membranes and to ghrelin receptor: towards a better understanding of the underlying mechanisms. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:2102-13. [PMID: 20637180 DOI: 10.1016/j.bbamem.2010.07.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 07/02/2010] [Accepted: 07/06/2010] [Indexed: 10/19/2022]
Abstract
The O-octanoylation of human ghrelin is a natural post-translational modification that enhances its binding to model membranes and could potentially play a central role in ghrelin biological activities. Here, we aimed to clarify the mechanisms that drive ghrelin to the membrane and hence to its receptor that mediates most of its endocrinological effects. As the acylation enhances ghrelin lipophilicity and that ghrelin contains many basic residues, we examined the electrostatic attraction and/or hydrophobic interactions with membranes. Using various liposomes and buffer conditions in binding, zeta potential and isothermal titration calorimetry studies, we found that whereas acylated and unacylated ghrelin were both electrostatically attracted towards the membrane, only acylated ghrelin penetrated into the headgroup and the lipid backbone regions of negatively charged membranes. The O-acylation induced a 120-fold increase in ghrelin local concentration in the membrane. However, acylated ghrelin did not deeply penetrate the membrane nor did it perturb its organisation. Conformational studies by circular dichroism and attenuated total reflection Fourier transformed infrared as well as in silico modelling revealed that both forms of ghrelin mainly adopted the same structure in aqueous, micellar and bilayer environments even though acylated ghrelin structure is slightly more α-helical in a lipid bilayer environment. Altogether our results suggest that membrane acts as a "catalyst" in acylated ghrelin binding to the ghrelin receptor and hence could explain why acylated and unacylated ghrelin are both full agonists of this receptor but in the nanomolar and micromolar range, respectively.
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Affiliation(s)
- Edith Staes
- Université catholique de Louvain, Unité de Pharmacie Galénique, 1200 Brussels, Belgium.
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Structure, evolutionary conservation, and conformational dynamics of Homo sapiens fascin-1, an F-actin crosslinking protein. J Mol Biol 2010; 400:589-604. [PMID: 20434460 DOI: 10.1016/j.jmb.2010.04.043] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Revised: 04/21/2010] [Accepted: 04/22/2010] [Indexed: 12/19/2022]
Abstract
Eukaryotes have several highly conserved actin-binding proteins that crosslink filamentous actin into compact ordered bundles present in distinct cytoskeletal processes, including microvilli, stereocilia and filopodia. Fascin is an actin-binding protein that is present predominantly in filopodia, which are believed to play a central role in normal and aberrant cell migration. An important outstanding question regards the molecular basis for the unique localization and functional properties of fascin compared with other actin crosslinking proteins. Here, we present the crystal structure of full-length Homo sapiens fascin-1, and examine its packing, conformational flexibility, and evolutionary sequence conservation. The structure reveals a novel arrangement of four tandem beta-trefoil domains that form a bi-lobed structure with approximate pseudo 2-fold symmetry. Each lobe has internal approximate pseudo 2-fold and pseudo 3-fold symmetry axes that are approximately perpendicular, with beta-hairpin triplets located symmetrically on opposite sides of each lobe that mutational data suggest are actin-binding domains. Sequence conservation analysis confirms the importance of hydrophobic core residues that stabilize the beta-trefoil fold, as well as interfacial residues that are likely to stabilize the overall fascin molecule. Sequence conservation also indicates highly conserved surface patches near the putative actin-binding domains of fascin, which conformational dynamics analysis suggests to be coupled via an allosteric mechanism that might have important functional implications for F-actin crosslinking by fascin.
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31
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Dennison SR, Kim YS, Cha HJ, Phoenix DA. Investigations into the ability of the peptide, HAL18, to interact with bacterial membranes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 38:37-43. [PMID: 18600320 DOI: 10.1007/s00249-008-0352-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Revised: 06/06/2008] [Accepted: 06/12/2008] [Indexed: 10/21/2022]
Abstract
Halocidin was isolated from hemocytes, Halocynthia aurantium as a heterodimeric peptide consisting of two alpha-helical subunits, Hal15 and Hal18. Hal18 was shown to have antibacterial properties against Bacillus subtilis (MLC = 15 microM) and Escherichia coli (MLC = 100 microM). The peptide was shown to produce stable monolayers, which were characteristic of alpha-helical peptides predicted to orientate parallel to the surface of the interface. Constant area assays showed that Hal18 was surface active (4 microM) inducing surface pressure changes >30 mN m(-1) characteristic of membrane interactive peptides. The peptide induced stable surface pressure changes in monolayers that were mimetic of B. subtilis membranes (circa 7 mN m(-1)) and E. coli membrane-mimics (circa 4 mN m(-1)). Hal18 inserted readily into zwitterionic DOPE and anionic DOPG monolayers inducing surface pressure changes circa 8 mN m(-1) in both cases, providing evidence that interaction is not headgroup specific. Thermodynamic analysis of compression isotherms showed that the presence of Hal18 destabilised B. subtilis membranes (DeltaG (Mix) > 0), which is in contrast to its stabilising effect on E. coli lipid extract implying the differential antimicrobial efficacy may be driven by lipid packing.
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Affiliation(s)
- Sarah R Dennison
- Faculty of Science and Technology, University of Central Lancashire, Preston, UK
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32
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Endocytosis and the Actin Cytoskeleton in Dictyostelium discoideum. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 267:343-97. [DOI: 10.1016/s1937-6448(08)00633-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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33
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Lomize AL, Pogozheva ID, Lomize MA, Mosberg HI. The role of hydrophobic interactions in positioning of peripheral proteins in membranes. BMC STRUCTURAL BIOLOGY 2007; 7:44. [PMID: 17603894 PMCID: PMC1934363 DOI: 10.1186/1472-6807-7-44] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Accepted: 06/29/2007] [Indexed: 02/05/2023]
Abstract
BACKGROUND Three-dimensional (3D) structures of numerous peripheral membrane proteins have been determined. Biological activity, stability, and conformations of these proteins depend on their spatial positions with respect to the lipid bilayer. However, these positions are usually undetermined. RESULTS We report the first large-scale computational study of monotopic/peripheral proteins with known 3D structures. The optimal translational and rotational positions of 476 proteins are determined by minimizing energy of protein transfer from water to the lipid bilayer, which is approximated by a hydrocarbon slab with a decadiene-like polarity and interfacial regions characterized by water-permeation profiles. Predicted membrane-binding sites, protein tilt angles and membrane penetration depths are consistent with spin-labeling, chemical modification, fluorescence, NMR, mutagenesis, and other experimental studies of 53 peripheral proteins and peptides. Experimental membrane binding affinities of peripheral proteins were reproduced in cases that did not involve a helix-coil transition, specific binding of lipids, or a predominantly electrostatic association. Coordinates of all examined peripheral proteins and peptides with the calculated hydrophobic membrane boundaries, subcellular localization, topology, structural classification, and experimental references are available through the Orientations of Proteins in Membranes (OPM) database. CONCLUSION Positions of diverse peripheral proteins and peptides in the lipid bilayer can be accurately predicted using their 3D structures that represent a proper membrane-bound conformation and oligomeric state, and have membrane binding elements present. The success of the implicit solvation model suggests that hydrophobic interactions are usually sufficient to determine the spatial position of a protein in the membrane, even when electrostatic interactions or specific binding of lipids are substantial. Our results demonstrate that most peripheral proteins not only interact with the membrane surface, but penetrate through the interfacial region and reach the hydrocarbon interior, which is consistent with published experimental studies.
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Affiliation(s)
- Andrei L Lomize
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109-1065, USA
| | - Irina D Pogozheva
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109-1065, USA
| | - Mikhail A Lomize
- College of Literature, Science and the Arts, University of Michigan, Ann Arbor, MI 48109-1065, USA
| | - Henry I Mosberg
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109-1065, USA
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Mihajlovic M, Lazaridis T. Calculations of pH-dependent binding of proteins to biological membranes. J Phys Chem B 2007; 110:3375-84. [PMID: 16494352 DOI: 10.1021/jp055906b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Binding of proteins to membranes is often accompanied by titration of ionizable residues and is, therefore, dependent on pH. We present a theoretical treatment and computational approach for predicting absolute, pH-dependent membrane binding free energies. The standard free energy of binding, DeltaG, is defined as -RTln(P(b)/P(f)), where P(b) and P(f) are the amounts of bound and free protein. The apparent pK(a) of binding is the pH value at which P(b) and P(f) are equal. Proteins bind to the membrane in the pH range where DeltaG is negative. The components of the binding free energy are (a) the free energy cost of ionization state changes (DeltaG(ion)), (b) the effective energy of transfer from solvent to the membrane surface, (c) the translational/rotational entropy cost of binding, and (d) an ideal entropy term that depends on the relative volume of the bound and free state and therefore depends on lipid concentration. Calculation of the first term requires determination of pK(a) values in solvent and on the membrane surface. All energies required by the method are obtained from molecular dynamics trajectories on an implicit membrane (IMM1-GC). The method is tested on pentalysine and the helical peptide VEEKS, derived from the membrane-binding domain of phosphocholine cytidylyltransferase. The agreement between the measured and the calculated free energies of binding of pentalysine is good. The extent of membrane binding of VEEKS is, however, underestimated compared to experiment. Calculations of the interaction energy between two VEEKS helices on the membrane suggest that the discrepancy is mainly due to the neglect of protein-protein interactions on the membrane surface.
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Affiliation(s)
- Maja Mihajlovic
- Department of Chemistry, City College of the City University of New York, New York, NY 10031, USA
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Meister A, Nicolini C, Waldmann H, Kuhlmann J, Kerth A, Winter R, Blume A. Insertion of lipidated Ras proteins into lipid monolayers studied by infrared reflection absorption spectroscopy (IRRAS). Biophys J 2006; 91:1388-401. [PMID: 16731561 PMCID: PMC1518660 DOI: 10.1529/biophysj.106.084624] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Accepted: 05/15/2006] [Indexed: 11/18/2022] Open
Abstract
Ras proteins have to be associated with the inner leaflet of the plasma membrane to perform their signaling functions. This membrane targeting and binding is controlled by post-translational covalent attachment of farnesyl and palmitoyl chains to cysteines in the membrane anchor region of the N- and H-Ras isoforms. Two N-Ras lipoproteins were investigated, namely a farnesylated and hexadecylated protein, presenting the natural hydrophobic modifications and a doubly hexadecylated construct, respectively. The proteins are surface active and form a Gibbs monolayer at the air-D2O interface. The contours of the amide-I bands were analyzed using infrared reflection absorption spectroscopy (IRRAS). Langmuir monolayers of a mixture of POPC, brain sphingomyelin, and cholesterol were used as half of a model biomembrane to study the insertion of these N-Ras proteins. They insert with their hydrophobic anchors into lipid monolayers but at higher surface pressures (30 mN/m); the farnesylated and hexadecylated protein desorbs completely from the monolayer, whereas the doubly hexadecylated protein remains incorporated. During the insertion process, changes in the orientation of the protein secondary structure were detected by comparison with simulated IRRA spectra, based on the information on the relative orientation of the secondary structure elements from the protein crystal structure data.
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Affiliation(s)
- Annette Meister
- Institut für Physikalische Chemie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
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Sengupta K, Limozin L, Tristl M, Haase I, Fischer M, Sackmann E. Coupling artificial actin cortices to biofunctionalized lipid monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:5776-85. [PMID: 16768508 DOI: 10.1021/la053310+] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We report the assembly of protein supramolecular structures at an air-water interface and coupling of artificial actin cortices to such structures. The coupling strategies adopted include electrostatic binding of actin to monolayers doped with lipids, exposing positively charged poly(ethylene glycol) headgroups; binding of biotinylated actin to lipids carrying biotin headgroups through avidin; binding of actin to membranes through biotinylated hisactophilin (a cellular actin-membrane coupler) using an avidin-biotin linkage; and coupling of actin to membranes carrying chelating lipids through a 15-nm-diameter protein capsid (bacterial lumazine synthase or LuSy) exhibiting histidine tags (which bind both to actin and to the chelating lipid). The distribution of the proteins in a direction normal to the interface was measured by neutron reflectivity under different conditions of pH and ionic strength. In the case of the first three binding methods, the thickness of the actin film was found to correspond to a single actin filament. Multilayers of actin could be formed only by using the multifunctional LuSy couplers that exhibit 60 hexahistidine tags and can thus act as actin cross-linkers. The LuSy-mediated binding can be reversibly switched by pH variations.
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Affiliation(s)
- Kheya Sengupta
- Lehrstuhl für Biophysik, E22, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching, Germany.
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Abstract
Prion protein fragments that are extracted from the brains of patients with Gerstmann-Straussler-Scheinker disease are known to have stimulating action on circulating leukocytes. In particular, the amyloidogenic hydrophobic prion peptide HuPrP (113-127) AGAAAAGAVVGGLGG has been reported to be associated with significant cellular toxicity. In this paper we show that the self assembled form of HuPrP (113-127) and its valine rich domains viz. GAVVGGLG [HuPrP (119-126)] and VVGGLGG [HuPrP (121-127)] are toxic to peripheral lymphocytes. To explore the cytotoxic mechanism of these fragments, we studied 3-(4,5-dimethylthiazol-2yl)-2-5-diphenyltetrazolium bromide (MTT) reduction, reactive oxygen species (ROS) generation, calcium influx and raft sequestration of' peptide treated lymphocytes. Langmuir monolayer studies on these peptides showed a maximum lipid perturbing property of HuPrP (121-127) as compared to the other two fragments. MTT reduction assays on lymphocytes treated with peptides indicated that the prion peptide fibrils are relatively more toxic than freshly solubilized peptide preparations. Lymphocytes treated with HuPrP (121-127), HuPrP (113-127) and HuPrP (119-126) fibrils underwent 60%, 30% and 40% cell death, respectively. Abeta(1-42), HuPrP (119-126) and HuPrP (121-127) fibrils caused 4 fold increases in intracellular ROS as compared with control cells. However, HuPrP (113-127) fibrils lacked such a significant ROS generating activity, indicating that a subtle difference in sequence leads to a difference in the toxic mechanism in the cell. HuPrP (119-126) and HuPrP (121-127) fibrils also produced maximum raft sequestration and calcium influx. Taken together, these data suggest that the assemblage of prion fragments has significant toxic activity on peripheral lymphocytes, a finding with implications for controlling reactive lymphocytes in prion infected subjects.
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Affiliation(s)
- Jayaraman Murali
- Bioorganic and Neurochemistry Laboratory, Central Leather Research Institute, Adyar, Chennai-600 020, India
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Gosavi S, Chavez LL, Jennings PA, Onuchic JN. Topological frustration and the folding of interleukin-1 beta. J Mol Biol 2005; 357:986-96. [PMID: 16469330 DOI: 10.1016/j.jmb.2005.11.074] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Revised: 11/18/2005] [Accepted: 11/23/2005] [Indexed: 11/24/2022]
Abstract
The cytokine, interleukin-1beta (IL-1beta), adopts a beta-trefoil fold. It is known to be much slower folding than similarly sized proteins, despite having a low contact order. Proteins are sufficiently well designed that their folding is not dominated by local energetic traps. Therefore, protein models that encode only the folded structure and are energetically unfrustrated (Gō-type), can capture the essentials of the folding routes. We investigate the folding thermodynamics of IL-1beta using such a model and molecular dynamics (MD) simulations. We develop an enhanced sampling technique (a modified multicanonical method) to overcome the sampling problem caused by the slow folding. We find that IL-1beta has a broad and high free energy barrier. In addition, the protein fold causes intermediate unfolding and refolding of some native contacts within the protein along the folding trajectory. This "backtracking" occurs around the barrier region. Complex folds like the beta-trefoil fold and functional loops like the beta-bulge of IL-1beta can make some of the configuration space unavailable to the protein and cause topological frustration.
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Affiliation(s)
- Shachi Gosavi
- Center for Theoretical Biological Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92037, USA
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39
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Lund M, Akesson T, Jönsson B. Enhanced protein adsorption due to charge regulation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:8385-8. [PMID: 16114946 DOI: 10.1021/la050607z] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
When a protein molecule approaches a charged surface, its protonation state can undergo dramatic changes due to the imposed electric potential. This has a large impact on adsorption strengths that may be enhanced by several kT. Using mesoscopic simulation techniques as well as analytical theories, we have investigated this regulation mechanism and demonstrate how it is influenced by salt concentration and solution pH. Using hisactophilin as a test case, we show how the binding to a lipid membrane is governed by small changes in pH and that this is intimately coupled to the charge regulation mechanism.
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Affiliation(s)
- Mikael Lund
- Theoretical Chemistry, Chemical Center, POB 124, S-221 00 Lund, Sweden.
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Patel H, Barber DL. A developmentally regulated Na-H exchanger in Dictyostelium discoideum is necessary for cell polarity during chemotaxis. ACTA ACUST UNITED AC 2005; 169:321-9. [PMID: 15851518 PMCID: PMC2171856 DOI: 10.1083/jcb.200412145] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Increased intracellular H+ efflux is speculated to be an evolutionarily conserved mechanism necessary for rapid assembly of cytoskeletal filaments and for morphological polarity during cell motility. In Dictyostelium discoideum, increased intracellular pH through undefined transport mechanisms plays a key role in directed cell movement. We report that a developmentally regulated Na-H exchanger in Dictyostelium discoideum (DdNHE1) localizes to the leading edge of polarized cells and is necessary for intracellular pH homeostasis and for efficient chemotaxis. Starved DdNHE1-null cells (Ddnhe1−) differentiate, and in response to the chemoattractant cAMP they retain directional sensing; however, they cannot attain a polarized morphology, but instead extend mislocalized pseudopodia around the cell and exhibit decreased velocity. Consistent with impaired polarity, in response to chemoattractant, Ddnhe1− cells lack a leading edge localization of F-actin and have significantly attenuated de novo F-actin polymerization but increased abundance of membrane-associated phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3). These findings indicate that during chemotaxis DdNHE1 is necessary for establishing the kinetics of actin polymerization and PI(3,4,5)P3 production and for attaining a polarized phenotype.
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Affiliation(s)
- Hitesh Patel
- Department of Cell and Tissue Biology, University of California, San Francisco, 4143, USA
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41
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Abstract
The amyloid beta (A beta) peptide is the major component found in the amyloid deposits in the brains of Alzheimer's disease patients. In vitro studies have demonstrated that the aggregation of A beta can take place at three orders of magnitude lower concentrations in the presence of phospholipid molecules compared to bulk peptide studies, suggesting that membrane lipids may mediate A beta toxicity. To understand the interaction of A beta with lipid membranes, we have examined A beta 40 with anionic dipalmitoylphosphatidylglycerol (DPPG), zwitterionic dipalmitoylphosphatidylcholine (DPPC), and cationic dipalmitoyltrimethylammonium propane (DPTAP) monolayers under different subphase conditions. We have used a constant surface pressure insertion assay to assess the degree of peptide insertion into the lipids. Simultaneously, we monitored the surface morphology of the monolayers with fluorescence microscopy. We have also performed dual-probe fluorescence measurements where both the peptide and lipid are tagged with chromophores. Isotherm measurements show that A beta inserts into both DPTAP and DPPG monolayers under physiologically relevant conditions. Insertion into DPPC occurs at lipid densities below that found in a bilayer. The level of insertion is inversely proportional to the lipid packing density. Our results indicate that lipids need not be anionic to interact with A beta. Electrostatic effects involved in A beta 40-lipid interaction are discussed.
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Affiliation(s)
- Canay Ege
- Department of Chemistry, The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
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Podell S, Gribskov M. Predicting N-terminal myristoylation sites in plant proteins. BMC Genomics 2004; 5:37. [PMID: 15202951 PMCID: PMC449705 DOI: 10.1186/1471-2164-5-37] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2004] [Accepted: 06/17/2004] [Indexed: 01/09/2023] Open
Abstract
Background N-terminal myristoylation plays a vital role in membrane targeting and signal transduction in plant responses to environmental stress. Although N-myristoyltransferase enzymatic function is conserved across plant, animal, and fungal kingdoms, exact substrate specificities vary, making it difficult to predict protein myristoylation accurately within specific taxonomic groups. Results A new method for predicting N-terminal myristoylation sites specifically in plants has been developed and statistically tested for sensitivity, specificity, and robustness. Compared to previously available methods, the new model is both more sensitive in detecting known positives, and more selective in avoiding false positives. Scores of myristoylated and non-myristoylated proteins are more widely separated than with other methods, greatly reducing ambiguity and the number of sequences giving intermediate, uninformative results. The prediction model is available at . Conclusion Superior performance of the new model is due to the selection of a plant-specific training set, covering 266 unique sequence examples from 40 different species, the use of a probability-based hidden Markov model to obtain predictive scores, and a threshold cutoff value chosen to provide maximum positive-negative discrimination. The new model has been used to predict 589 plant proteins likely to contain N-terminal myristoylation signals, and to analyze the functional families in which these proteins occur.
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Affiliation(s)
- Sheila Podell
- San Diego Supercomputer Center, University of California San Diego, La Jolla CA 92093-0537, USA
- Department of Biology, University of California San Diego, La Jolla CA 92093-0537, USA
| | - Michael Gribskov
- San Diego Supercomputer Center, University of California San Diego, La Jolla CA 92093-0537, USA
- Department of Biology, University of California San Diego, La Jolla CA 92093-0537, USA
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Gerebtzoff G, Li-Blatter X, Fischer H, Frentzel A, Seelig A. Halogenation of Drugs Enhances Membrane Binding and Permeation. Chembiochem 2004; 5:676-84. [PMID: 15122640 DOI: 10.1002/cbic.200400017] [Citation(s) in RCA: 183] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Halogenation of drugs is commonly used to enhance membrane binding and permeation. We quantify the effect of replacing a hydrogen residue by a chlorine or a trifluoromethyl residue in position C-2 of promazine, perazine, and perphenazine analogues. Moreover, we investigate the influence of the position (C-6 and C-7) of residue CF(3) in benzopyranols. The twelve drugs are characterized by surface activity measurements, which yield the cross-sectional area, the air-water partition coefficient, and the critical micelle concentration. By using the first two parameters (A(D) and K(aw)) and the appropriate membrane packing density, the lipid-water partition coefficients, are calculated in excellent agreement with the lipid-water partition coefficients measured by means of isothermal titration calorimetry for small unilamellar vesicles of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. Replacement of a hydrogen residue by a chlorine and a trifluoromethyl residue enhances the free energy of partitioning into the lipid membrane, on average by deltaG(lw) approximately -1.3 or -4.5 kJ mol(-1), respectively, and the permeability coefficient by a factor of approximately 2 or approximately 9, respectively. Despite exhibiting practically identical hydrophobicities, the two benzopyranol analogues differ in their permeability coefficients by almost an order of magnitude; this is due to their different cross-sectional areas at the air-water and lipid-water interfaces.
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Affiliation(s)
- Grégori Gerebtzoff
- Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
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Li C, Franklin JL, Graves-Deal R, Jerome WG, Cao Z, Coffey RJ. Myristoylated Naked2 escorts transforming growth factor alpha to the basolateral plasma membrane of polarized epithelial cells. Proc Natl Acad Sci U S A 2004; 101:5571-6. [PMID: 15064403 PMCID: PMC397424 DOI: 10.1073/pnas.0401294101] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2003] [Indexed: 12/20/2022] Open
Abstract
The epidermal growth factor receptor ligands transforming growth factor alpha (TGF alpha) and amphiregulin are delivered to the basolateral surface of polarized epithelial cells where they are cleaved by TACE/ADAM17. Basolateral sorting information resides in their cytoplasmic tail domains, but tail-interacting proteins required for basolateral trafficking have not been identified. Naked (NKD)1 and NKD2 are mammalian homologs of Drosophila Naked Cuticle, which negatively regulates canonical Wnt signaling by binding Dishevelled. We present evidence that NKD2, but not NKD1, binds to basolateral sorting motifs in the cytoplasmic tail of TGF alpha. Processing and cell-surface delivery of TGF alpha are accelerated in NKD2-overexpressing Madin-Darby canine kidney cells. NKD2 is myristoylated on glycine, the second residue. On expression of myristoylation-defective (G2A) NKD2, neither NKD2 nor TGF alpha appears at the basolateral plasma membrane of polarized Madin-Darby canine kidney cells; however, membrane staining for TGF alpha is restored on silencing expression of this mutant NKD2. Amphiregulin does not interact with NKD2 and retains its basolateral localization in G2A-NKD2-expressing cells, as do Na(+), K(+) ATPase alpha 1 and E-cadherin. These data identify an unexpected function for NKD2, i.e., myristoylation-dependent escort of TGF alpha to the basolateral plasma membrane of polarized epithelial cells.
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Affiliation(s)
- Cunxi Li
- Department of Medicine, Vanderbilt University Medical Center and Department of Veterans Affairs Medical Center, Nashville, TN 37232-2279, USA
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45
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Hanakam F, Gerisch G. Monitoring intracellular shutting of histidine-rich pH sensor proteins tagged with green fluorescent protein. Methods Enzymol 2003; 302:51-8. [PMID: 12876762 DOI: 10.1016/s0076-6879(99)02009-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Affiliation(s)
- F Hanakam
- Micromet GmbH, D-82152 Martinsried, Germany
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46
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Benedetti CE, Kobarg J, Pertinhez TA, Gatti RM, de Souza ON, Spisni A, Meneghini R. Plasmodium falciparum histidine-rich protein II binds to actin, phosphatidylinositol 4,5-bisphosphate and erythrocyte ghosts in a pH-dependent manner and undergoes coil-to-helix transitions in anionic micelles. Mol Biochem Parasitol 2003; 128:157-66. [PMID: 12742582 DOI: 10.1016/s0166-6851(03)00057-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The recombinant histidine-rich protein II (HRPII) from Plasmodium falciparum was shown to bind actin and phosphatidylinositol 4,5-bisphosphate (PIP(2)) in vitro in a pH-dependent manner, very similar to hisactophilin, an actin-binding protein from ameba. Binding of HRPII to actin and PIP(2) occurred at pH 6.0 and 6.5, but not above pH 7.0. Circular dichroism (CD) spectroscopy confirmed that HRPII interacts with actin at pH below 7.0, as judged by the changes induced in the secondary structure of the HRPII/actin mixture. Further CD analysis demonstrated that HRPII adopts a predominantly alpha-helical conformation with anionic micelles of PIP(2) and SDS, but not with neutral micelles of phosphatidylcholine (PC), a feature that is common to many actin-binding proteins involved in cytoskeleton remodeling. Similarly to hisactophilin, a GFP-HRPII fusion protein shuttled from the cytoplasm to the nucleus of HeLa cells as the cellular pH was lowered from 8.0 to 6.0. HeLa cells transfected with the HRPII gene showed increased levels of histidine-rich proteins (HRPs) in the soluble cell fraction at pH 8.0. At pH 6.0, however, HRPs were detected mainly in the insoluble cell fraction. Interestingly, we found that HRPII binds to human erythrocyte membranes at pH 6.0 and 6.5 but not at pH above 7.0. Our results point to remarkable similarities between HRPII, hisactophilin, and actin-binding proteins. Possible roles of the HRPII during Plasmodium infection are discussed in the light of these findings.
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Affiliation(s)
- Celso Eduardo Benedetti
- Centro de Biologia Molecular Estrutural (CEBIME), Laboratório Nacional de Luz Sincrotron (LNLS), CP6192, Campinas, SP CEP 13084-971, Brazil.
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Johnson JE, Xie M, Singh LMR, Edge R, Cornell RB. Both acidic and basic amino acids in an amphitropic enzyme, CTP:phosphocholine cytidylyltransferase, dictate its selectivity for anionic membranes. J Biol Chem 2003; 278:514-22. [PMID: 12401806 DOI: 10.1074/jbc.m206072200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amphitropic proteins are regulated by reversible membrane interaction. Anionic phospholipids generally promote membrane binding of such proteins via electrostatics between the negatively charged lipid headgroups and clusters of basic groups on the proteins. In this study of one amphitropic protein, a cytidylyltransferase (CT) that regulates phosphatidylcholine synthesis, we found that substitution of lysines to glutamine along both interfacial strips of the membrane-binding amphipathic helix eliminated electrostatic binding. Unexpectedly, three glutamates also participate in the selectivity for anionic membrane surfaces. These glutamates become protonated in the low pH milieu at the surface of anionic, but not zwitterionic membranes, increasing protein positive charge and hydrophobicity. The binding and insertion into lipid vesicles of a synthetic peptide containing the three glutamates was pH-dependent with an apparent pK(a) that varied with anionic lipid content. Glutamate to glutamine substitution eliminated the pH dependence of the membrane interaction, and reduced anionic membrane selectivity of both the peptide and the whole CT enzyme examined in cells. Thus anionic lipids, working via surface-localized pH effects, can promote membrane binding by modifying protein charge and hydrophobicity, and this novel mechanism contributes to the membrane selectivity of CT in vivo.
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Affiliation(s)
- Joanne E Johnson
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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48
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Pintsch T, Zischka H, Schuster SC. Hisactophilin is involved in osmoprotection in Dictyostelium. BMC BIOCHEMISTRY 2002; 3:10. [PMID: 11996675 PMCID: PMC115871 DOI: 10.1186/1471-2091-3-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2001] [Accepted: 05/07/2002] [Indexed: 11/30/2022]
Abstract
BACKGROUND Dictyostelium cells exhibit an unusual stress response as they protect themselves against hyperosmotic stress. Cytoskeletal proteins are recruited from the cytosolic pool to the cell cortex, thereby reinforcing it. In order to gain more insight into the osmoprotective mechanisms of this amoeba, we used 1-D and 2-D gel electrophoresis to identify new proteins that are translocated during osmotic shock. RESULTS We identified hisactophilin as one of the proteins that are enriched in the cytoskeletal fraction during osmotic shock. In mutants lacking hisactophilin, viability is reduced under hyperosmotic stress conditions. In wild type cells, serine phosphorylation of hisactophilin was specifically induced by hypertonicity, but not when other stress conditions were imposed on cells. The phosphorylation kinetics reveals a slow accumulation of phosphorylated hisactophilin from 20-60 min after onset of the hyperosmotic shock condition. CONCLUSION In the present study, we identified hisactophilin as an essential protein for the osmoprotection of Dictyostelium cells. The observed phosphorylation kinetics suggest that hisactophilin regulation is involved in long-term osmoprotection and that phosphorylation occurs in parallel with inactivation of the dynamic actin cytoskeleton.
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Affiliation(s)
- Tanja Pintsch
- Max-Planck-Institute for Biochemistry, 82152 Martinsried, Germany
- SWITCH Biotech AG, Fraunhoferstr. 10, 82152 Martinsried, Germany
| | - Hans Zischka
- Max-Planck-Institute for Biochemistry, 82152 Martinsried, Germany
- GSF – Forschungszentrum für Umwelt und Gesundheit, GmbH Ingolstädter Landstraβe 1, D-85764 Neuherberg
| | - Stephan C Schuster
- Max-Planck-Institute for Biochemistry, 82152 Martinsried, Germany
- Max-Planck-Institute for Developmental Biology, Spemannstr. 35, 72076 Tübingen, Germany
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49
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Lipidated peptides as tools for understanding the membrane interactions of lipid-modified proteins. PEPTIDE-LIPID INTERACTIONS 2002. [DOI: 10.1016/s1063-5823(02)52015-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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50
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The Chemistry of Movement. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50022-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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