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Palaniappan C, Rajendran S, Sekar K. Alternate conformations found in protein structures implies biological functions: A case study using cyclophilin A. Curr Res Struct Biol 2024; 7:100145. [PMID: 38690327 PMCID: PMC11059445 DOI: 10.1016/j.crstbi.2024.100145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 03/16/2024] [Accepted: 04/15/2024] [Indexed: 05/02/2024] Open
Abstract
Protein dynamics linked to numerous biomolecular functions, such as ligand binding, allosteric regulation, and catalysis, must be better understood at the atomic level. Reactive atoms of key residues drive a repertoire of biomolecular functions by flipping between alternate conformations or conformational substates, seldom found in protein structures. Probing such sparsely sampled alternate conformations would provide mechanistic insight into many biological functions. We are therefore interested in evaluating the instance of amino acids adopted alternate conformations, either in backbone or side-chain atoms or in both. Accordingly, over 70000 protein structures appear to contain alternate conformations only 'A' and 'B' for any atom, particularly the instance of amino acids that adopted alternate conformations are more for Arg, Cys, Met, and Ser than others. The resulting protein structure analysis depicts that amino acids with alternate conformations are mainly found in the helical and β-regions and are often seen in high-resolution X-ray crystal structures. Furthermore, a case study on human cyclophilin A (CypA) was performed to explain the pre-existing intrinsic dynamics of catalytically critical residues from the CypA and how such intrinsic dynamics perturbed upon Ser99Thr mutation using molecular dynamics simulations on the ns-μs timescale. Simulation results demonstrated that the Ser99Thr mutation had impaired the alternate conformations or the catalytically productive micro-environment of Phe113, mimicking the experimentally observed perturbation captured by X-ray crystallography. In brief, a deeper comprehension of alternate conformations adopted by the amino acids may shed light on the interplay between protein structure, dynamics, and function.
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Affiliation(s)
- Chandrasekaran Palaniappan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
- Department of Computational and Data Sciences, Indian Institute of Science, Bangalore, 560012, India
| | - Santhosh Rajendran
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
- Department of Computational and Data Sciences, Indian Institute of Science, Bangalore, 560012, India
| | - Kanagaraj Sekar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
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Greisman JB, Dalton KM, Brookner DE, Klureza MA, Sheehan CJ, Kim IS, Henning RW, Russi S, Hekstra DR. Perturbative diffraction methods resolve a conformational switch that facilitates a two-step enzymatic mechanism. Proc Natl Acad Sci U S A 2024; 121:e2313192121. [PMID: 38386706 PMCID: PMC10907320 DOI: 10.1073/pnas.2313192121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 12/18/2023] [Indexed: 02/24/2024] Open
Abstract
Enzymes catalyze biochemical reactions through precise positioning of substrates, cofactors, and amino acids to modulate the transition-state free energy. However, the role of conformational dynamics remains poorly understood due to poor experimental access. This shortcoming is evident with Escherichia coli dihydrofolate reductase (DHFR), a model system for the role of protein dynamics in catalysis, for which it is unknown how the enzyme regulates the different active site environments required to facilitate proton and hydride transfer. Here, we describe ligand-, temperature-, and electric-field-based perturbations during X-ray diffraction experiments to map the conformational dynamics of the Michaelis complex of DHFR. We resolve coupled global and local motions and find that these motions are engaged by the protonated substrate to promote efficient catalysis. This result suggests a fundamental design principle for multistep enzymes in which pre-existing dynamics enable intermediates to drive rapid electrostatic reorganization to facilitate subsequent chemical steps.
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Affiliation(s)
- Jack B. Greisman
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA02138
| | - Kevin M. Dalton
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA02138
| | - Dennis E. Brookner
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA02138
| | - Margaret A. Klureza
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA02138
| | - Candice J. Sheehan
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA02138
| | - In-Sik Kim
- BioCARS, Argonne National Laboratory, The University of Chicago, Lemont, IL60439
| | - Robert W. Henning
- BioCARS, Argonne National Laboratory, The University of Chicago, Lemont, IL60439
| | - Silvia Russi
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA94025
| | - Doeke R. Hekstra
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA02138
- School of Engineering & Applied Sciences, Harvard University, Allston, MA02134
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Thompson MC. Combining temperature perturbations with X-ray crystallography to study dynamic macromolecules: A thorough discussion of experimental methods. Methods Enzymol 2023; 688:255-305. [PMID: 37748829 DOI: 10.1016/bs.mie.2023.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Temperature is an important state variable that governs the behavior of microscopic systems, yet crystallographers rarely exploit temperature changes to study the structure and dynamics of biological macromolecules. In fact, approximately 90% of crystal structures in the Protein Data Bank were determined under cryogenic conditions, because sample cryocooling makes crystals robust to X-ray radiation damage and facilitates data collection. On the other hand, cryocooling can introduce artifacts into macromolecular structures, and can suppress conformational dynamics that are critical for function. Fortunately, recent advances in X-ray detector technology, X-ray sources, and computational data processing algorithms make non-cryogenic X-ray crystallography easier and more broadly applicable than ever before. Without the reliance on cryocooling, high-resolution crystallography can be combined with various temperature perturbations to gain deep insight into the conformational landscapes of macromolecules. This Chapter reviews the historical reasons for the prevalence of cryocooling in macromolecular crystallography, and discusses its potential drawbacks. Next, the Chapter summarizes technological developments and methodologies that facilitate non-cryogenic crystallography experiments. Finally, the chapter discusses the theoretical underpinnings and practical aspects of multi-temperature and temperature-jump crystallography experiments, which are powerful tools for understanding the relationship between the structure, dynamics, and function of proteins and other biological macromolecules.
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Affiliation(s)
- Michael C Thompson
- Department of Chemistry and Biochemistry, University of California, Merced, Merced, CA, United States.
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Besaw JE, Miller RJD. Addressing high excitation conditions in time-resolved X-ray diffraction experiments and issues of biological relevance. Curr Opin Struct Biol 2023; 81:102624. [PMID: 37331203 DOI: 10.1016/j.sbi.2023.102624] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 05/16/2023] [Accepted: 05/16/2023] [Indexed: 06/20/2023]
Abstract
One of the most important fundamental questions connecting chemistry to biology is how chemistry scales in complexity up to biological systems where there are innumerable possible pathways and competing processes. With the development of ultrabright electron and x-ray sources, it has been possible to literally light up atomic motions to directly observe the reduction in dimensionality in the barrier crossing region to a few key reaction modes. How do these chemical processes further couple to the surrounding protein or macromolecular assembly to drive biological functions? Optical methods to trigger photoactive biological processes are needed to probe this issue on the relevant timescales. However, the excitation conditions have been in the highly nonlinear regime, which questions the biological relevance of the observed structural dynamics.
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Affiliation(s)
- Jessica E Besaw
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
| | - R J Dwayne Miller
- Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada.
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5
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Greisman JB, Dalton KM, Brookner DE, Klureza MA, Sheehan CJ, Kim IS, Henning RW, Russi S, Hekstra DR. Resolving conformational changes that mediate a two-step catalytic mechanism in a model enzyme. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.02.543507. [PMID: 37398233 PMCID: PMC10312612 DOI: 10.1101/2023.06.02.543507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Enzymes catalyze biochemical reactions through precise positioning of substrates, cofactors, and amino acids to modulate the transition-state free energy. However, the role of conformational dynamics remains poorly understood due to lack of experimental access. This shortcoming is evident with E. coli dihydrofolate reductase (DHFR), a model system for the role of protein dynamics in catalysis, for which it is unknown how the enzyme regulates the different active site environments required to facilitate proton and hydride transfer. Here, we present ligand-, temperature-, and electric-field-based perturbations during X-ray diffraction experiments that enable identification of coupled conformational changes in DHFR. We identify a global hinge motion and local networks of structural rearrangements that are engaged by substrate protonation to regulate solvent access and promote efficient catalysis. The resulting mechanism shows that DHFR's two-step catalytic mechanism is guided by a dynamic free energy landscape responsive to the state of the substrate.
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Affiliation(s)
- Jack B. Greisman
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA, United States
| | - Kevin M. Dalton
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA, United States
| | - Dennis E. Brookner
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA, United States
| | - Margaret A. Klureza
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA, United States
| | - Candice J. Sheehan
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA, United States
| | - In-Sik Kim
- BioCARS, The University of Chicago, Argonne National Laboratory, Lemont, IL, United States
| | - Robert W. Henning
- BioCARS, The University of Chicago, Argonne National Laboratory, Lemont, IL, United States
| | - Silvia Russi
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, United States
| | - Doeke R. Hekstra
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA, United States
- School of Engineering & Applied Sciences, Harvard University, Allston, MA, United States
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Thorne RE. Determining biomolecular structures near room temperature using X-ray crystallography: concepts, methods and future optimization. Acta Crystallogr D Struct Biol 2023; 79:78-94. [PMID: 36601809 PMCID: PMC9815097 DOI: 10.1107/s2059798322011652] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 12/04/2022] [Indexed: 01/05/2023] Open
Abstract
For roughly two decades, cryocrystallography has been the overwhelmingly dominant method for determining high-resolution biomolecular structures. Competition from single-particle cryo-electron microscopy and micro-electron diffraction, increased interest in functionally relevant information that may be missing or corrupted in structures determined at cryogenic temperature, and interest in time-resolved studies of the biomolecular response to chemical and optical stimuli have driven renewed interest in data collection at room temperature and, more generally, at temperatures from the protein-solvent glass transition near 200 K to ∼350 K. Fischer has recently reviewed practical methods for room-temperature data collection and analysis [Fischer (2021), Q. Rev. Biophys. 54, e1]. Here, the key advantages and physical principles of, and methods for, crystallographic data collection at noncryogenic temperatures and some factors relevant to interpreting the resulting data are discussed. For room-temperature data collection to realize its potential within the structural biology toolkit, streamlined and standardized methods for delivering crystals prepared in the home laboratory to the synchrotron and for automated handling and data collection, similar to those for cryocrystallography, should be implemented.
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Affiliation(s)
- Robert E. Thorne
- Physics Department, Cornell University, Ithaca, NY 14853, USA
- MiTeGen LLC, PO Box 3867, Ithaca, NY 14850, USA
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Plapp BV, Gakhar L, Subramanian R. Dependence of crystallographic atomic displacement parameters on temperature (25-150 K) for complexes of horse liver alcohol dehydrogenase. Acta Crystallogr D Struct Biol 2022; 78:1221-1234. [PMID: 36189742 PMCID: PMC9527765 DOI: 10.1107/s2059798322008361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 08/22/2022] [Indexed: 11/19/2022] Open
Abstract
Enzymes catalyze reactions by binding and orienting substrates with dynamic interactions. Horse liver alcohol dehydrogenase catalyzes hydrogen transfer with quantum-mechanical tunneling that involves fast motions in the active site. The structures and B factors of ternary complexes of the enzyme with NAD+ and 2,3,4,5,6-pentafluorobenzyl alcohol or NAD+ and 2,2,2-trifluoroethanol were determined to 1.1-1.3 Å resolution below the `glassy transition' in order to extract information about the temperature-dependent harmonic motions, which are reflected in the crystallographic B factors. The refinement statistics and structures are essentially the same for each structure at all temperatures. The B factors were corrected for a small amount of radiation decay. The overall B factors for the complexes are similar (13-16 Å2) over the range 25-100 K, but increase somewhat at 150 K. Applying TLS refinement to remove the contribution of pseudo-rigid-body displacements of coenzyme binding and catalytic domains provided residual B factors of 7-10 Å2 for the overall complexes and of 5-10 Å2 for C4N of NAD+ and the methylene carbon of the alcohols. These residual B factors have a very small dependence on temperature and include local harmonic motions and apparently contributions from other sources. Structures at 100 K show complexes that are poised for hydrogen transfer, which involves atomic displacements of ∼0.3 Å and is compatible with the motions estimated from the residual B factors and molecular-dynamics simulations. At 298 K local conformational changes are also involved in catalysis, as enzymes with substitutions of amino acids in the substrate-binding site have similar positions of NAD+ and pentafluorobenzyl alcohol and similar residual B factors, but differ by tenfold in the rate constants for hydride transfer.
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Affiliation(s)
- Bryce V. Plapp
- Department of Biochemistry and Molecular Biology, The University of Iowa, Iowa City, IA 52252, USA
| | - Lokesh Gakhar
- Protein and Crystallography Facility, Carver College of Medicine, The University of Iowa, Iowa City, IA 52252, USA
| | - Ramaswamy Subramanian
- Department of Biochemistry and Molecular Biology, The University of Iowa, Iowa City, IA 52252, USA
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Mohammadi S, Rafii-Tabar H, Sasanpour P. A modeling study of the effect of an alternating magnetic field on magnetite nanoparticles in proximity of the neuronal microtubules: A proposed mechanism for detachment of tau proteins. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 222:106913. [PMID: 35738092 DOI: 10.1016/j.cmpb.2022.106913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 05/17/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND AND OBJECTIVE It is known that the disintegration of microtubules in neurons occurs in response to the phosphorylation of the tau proteins that promotes the structural instability of the microtubules, as one of the factors underlying the onset of Alzheimer's disease (AD). METHODS In this study, the mechanical variations undergone by the tau protein's and microtubule's structures due to the action of intrinsic magnetite nanoparticles inside the brain tissue have been computationally modeled using the finite element (FEM) method. RESULTS The von Mises stress induced by magnetite nanoparticles, subject to an applied alternating magnetic field, leads to local heating and mechanical forces, prompting a corresponding deformation in, and displacement of, the microtubule and the tau protein. CONCLUSIONS The induction of these deformations would increase the probability of the microtubules' depolymerization, and hence their eventual structural disintegration.
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Affiliation(s)
- Simah Mohammadi
- Department of Medical Physics & Biomedical Engineering, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Hashem Rafii-Tabar
- Department of Medical Physics & Biomedical Engineering, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; The Physics Branch of Iran Academy of Sciences, Tehran, Iran.
| | - Pezhman Sasanpour
- Department of Medical Physics & Biomedical Engineering, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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10
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Ravikumar A, Gopnarayan MN, Subramaniam S, Srinivasan N. Comparison of side-chain dispersion in protein structures determined by cryo-EM and X-ray crystallography. IUCRJ 2022; 9:98-103. [PMID: 35059214 PMCID: PMC8733892 DOI: 10.1107/s2052252521011945] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 11/10/2021] [Indexed: 06/14/2023]
Abstract
An evaluation of systematic differences in local structure and conformation in the interior of protein tertiary structures determined by crystallography and by cryo-electron microscopy (cryo-EM) is reported. The expectation is that any consistent differences between the derived atomic models could provide insights into variations in side-chain packing that result from differences in specimens prepared for analysis between these two methods. By computing an atomic packing score, which provides a quantitative measure of clustering of side-chain atoms in the core of the tertiary structures, it is found that, in general, for structures determined by cryo-EM, side chains are more dispersed than in structures determined by X-ray crystallography over a similar resolution range. This trend is also observed in the packing comparison at subunit interfaces. Similar trends were observed in the packing comparison at the core of tertiary structures of the same proteins determined by both X-ray and cryo-EM methods. It is proposed here that the reduced dispersion of side chains in protein crystals could be due to some level of dehydration in 3D crystals prepared for X-ray crystallography and also because the higher rate of freezing of protein samples for cryo-EM may enable preservation of a more native conformation.
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Affiliation(s)
- Ashraya Ravikumar
- Molecular Biophysics Unit, Indian Institute of Science, Bengaluru, India
| | | | - Sriram Subramaniam
- University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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Stachowski TR, Snell ME, Snell EH. A SAXS-based approach to rationally evaluate radical scavengers - toward eliminating radiation damage in solution and crystallographic studies. JOURNAL OF SYNCHROTRON RADIATION 2021; 28:1309-1320. [PMID: 34475280 PMCID: PMC8415334 DOI: 10.1107/s1600577521004045] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 04/15/2021] [Indexed: 05/30/2023]
Abstract
X-ray-based techniques are a powerful tool in structural biology but the radiation-induced chemistry that results can be detrimental and may mask an accurate structural understanding. In the crystallographic case, cryocooling has been employed as a successful mitigation strategy but also has its limitations including the trapping of non-biological structural states. Crystallographic and solution studies performed at physiological temperatures can reveal otherwise hidden but relevant conformations, but are limited by their increased susceptibility to radiation damage. In this case, chemical additives that scavenge the species generated by radiation can mitigate damage but are not always successful and the mechanisms are often unclear. Using a protein designed to undergo a large-scale structural change from breakage of a disulfide bond, radiation damage can be monitored with small-angle X-ray scattering. Using this, we have quantitatively evaluated how three scavengers commonly used in crystallographic experiments - sodium nitrate, cysteine, and ascorbic acid - perform in solution at 10°C. Sodium nitrate was the most effective scavenger and completely inhibited fragmentation of the disulfide bond at a lower concentration (500 µM) compared with cysteine (∼5 mM) while ascorbic acid performed best at 5 mM but could only reduce fragmentation by ∼75% after a total accumulated dose of 792 Gy. The relative effectiveness of each scavenger matches their reported affinities for solvated electrons. Saturating concentrations of each scavenger shifted fragmentation from first order to a zeroth-order process, perhaps indicating the direct contribution of photoabsorption. The SAXS-based method can detect damage at X-ray doses far lower than those accessible crystallographically, thereby providing a detailed picture of scavenger processes. The solution results are also in close agreement with what is known about scavenger performance and mechanism in a crystallographic setting and suggest that a link can be made between the damage phenomenon in the two scenarios. Therefore, our engineered approach might provide a platform for more systematic and comprehensive screening of radioprotectants that can directly inform mitigation strategies for both solution and crystallographic experiments, while also clarifying fundamental radiation damage mechanisms.
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Affiliation(s)
- Timothy R. Stachowski
- Hauptman-Woodward Medical Research Institute, 700 Ellicott St, Buffalo, NY 14203, USA
- Cell Stress Biology, Roswell Park Comprehensive Cancer Center, 665 Elm Street, Buffalo, NY 14203, USA
| | - Mary E. Snell
- Hauptman-Woodward Medical Research Institute, 700 Ellicott St, Buffalo, NY 14203, USA
| | - Edward H. Snell
- Hauptman-Woodward Medical Research Institute, 700 Ellicott St, Buffalo, NY 14203, USA
- Materials Design and Innovation, State University at New York at Buffalo, 700 Ellicott St, Buffalo, NY 14203, USA
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12
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Chen J, Gong NJ, Chaim KT, Otaduy MCG, Liu C. Decompose quantitative susceptibility mapping (QSM) to sub-voxel diamagnetic and paramagnetic components based on gradient-echo MRI data. Neuroimage 2021; 242:118477. [PMID: 34403742 PMCID: PMC8720043 DOI: 10.1016/j.neuroimage.2021.118477] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/13/2021] [Indexed: 12/31/2022] Open
Abstract
PURPOSE A method named DECOMPOSE-QSM is developed to decompose bulk susceptibility measured with QSM into sub-voxel paramagnetic and diamagnetic components based on a three-pool complex signal model. METHODS Multi-echo gradient echo signal is modeled as a summation of three weighted exponentials corresponding to three types of susceptibility sources: reference susceptibility, diamagnetic and paramagnetic susceptibility relative to the reference. Paramagnetic component susceptibility (PCS) and diamagnetic component susceptibility (DCS) maps are constructed to represent the sub-voxel compartments by solving for linear and nonlinear parameters in the model. RESULTS Numerical forward simulation and phantom validation confirmed the ability of DECOMPOSE-QSM to separate the mixture of paramagnetic and diamagnetic components. The PCS obtained from temperature-variant brainstem imaging follows the Curie's Law, which further validated the model and the solver. Initial in vivo investigation of human brain images showed the ability to extract sub-voxel PCS and DCS sources that produce visually enhanced contrast between brain structures comparing to threshold QSM.
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Affiliation(s)
- Jingjia Chen
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, USA
| | - Nan-Jie Gong
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, USA; Vector Lab for Intelligent Medical Imaging and Neural Engineering, International Innovation Center of Tsinghua University, Shanghai, China
| | - Khallil Taverna Chaim
- LIM44, Instituto e Departamento de Radiologia, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, Brazil
| | | | - Chunlei Liu
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, USA.
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Snell EH, Helliwell JR. Microgravity as an environment for macromolecular crystallization – an outlook in the era of space stations and commercial space flight. CRYSTALLOGR REV 2021. [DOI: 10.1080/0889311x.2021.1900833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- E. H. Snell
- Hauptman-Woodward Medical Research Institute, Buffalo, NY, USA
- Materials Design and Innovation Department, SUNY Buffalo, Buffalo, NY, USA
| | - J. R. Helliwell
- Chemistry Department, University of Manchester, Manchester, UK
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14
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Reid KM, Yu X, Leitner DM. Change in vibrational entropy with change in protein volume estimated with mode Grüneisen parameters. J Chem Phys 2021; 154:055102. [DOI: 10.1063/5.0039175] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Affiliation(s)
- Korey M. Reid
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA
| | - Xin Yu
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA
| | - David M. Leitner
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA
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15
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McGregor L, Földes T, Bui S, Moulin M, Coquelle N, Blakeley MP, Rosta E, Steiner RA. Joint neutron/X-ray crystal structure of a mechanistically relevant complex of perdeuterated urate oxidase and simulations provide insight into the hydration step of catalysis. IUCRJ 2021; 8:46-59. [PMID: 33520242 PMCID: PMC7792999 DOI: 10.1107/s2052252520013615] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 10/12/2020] [Indexed: 06/12/2023]
Abstract
Cofactor-independent urate oxidase (UOX) is an ∼137 kDa tetrameric enzyme essential for uric acid (UA) catabolism in many organisms. UA is first oxidized by O2 to de-hydro-isourate (DHU) via a peroxo intermediate. DHU then undergoes hydration to 5-hy-droxy-isourate (5HIU). At different stages of the reaction both catalytic O2 and water occupy the 'peroxo hole' above the organic substrate. Here, high-resolution neutron/X-ray crystallographic analysis at room temperature has been integrated with molecular dynamics simulations to investigate the hydration step of the reaction. The joint neutron/X-ray structure of perdeuterated Aspergillus flavus UOX in complex with its 8-azaxanthine (8AZA) inhibitor shows that the catalytic water molecule (W1) is present in the peroxo hole as neutral H2O, oriented at 45° with respect to the ligand. It is stabilized by Thr57 and Asn254 on different UOX protomers as well as by an O-H⋯π interaction with 8AZA. The active site Lys10-Thr57 dyad features a charged Lys10-NH3 + side chain engaged in a strong hydrogen bond with Thr57OG1, while the Thr57OG1-HG1 bond is rotationally dynamic and oriented toward the π system of the ligand, on average. Our analysis offers support for a mechanism in which W1 performs a nucleophilic attack on DHUC5 with Thr57HG1 central to a Lys10-assisted proton-relay system. Room-temperature crystallography and simulations also reveal conformational heterogeneity for Asn254 that modulates W1 stability in the peroxo hole. This is proposed to be an active mechanism to facilitate W1/O2 exchange during catalysis.
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Affiliation(s)
- Lindsay McGregor
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London SE1 1UL, United Kingdom
- Large Scale Structures Group, Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Cedex 9, Grenoble, France
| | - Tamás Földes
- Department of Chemistry, King’s College London, London SE1 1DB, United Kingdom
- Department of Physics and Astronomy, University College, London WC1E 6BT, United Kingdom
| | - Soi Bui
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London SE1 1UL, United Kingdom
| | - Martine Moulin
- Life Sciences Group, Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Cedex 9, Grenoble, France
| | - Nicolas Coquelle
- Large Scale Structures Group, Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Cedex 9, Grenoble, France
| | - Matthew P. Blakeley
- Large Scale Structures Group, Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Cedex 9, Grenoble, France
| | - Edina Rosta
- Department of Chemistry, King’s College London, London SE1 1DB, United Kingdom
- Department of Physics and Astronomy, University College, London WC1E 6BT, United Kingdom
| | - Roberto A. Steiner
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London SE1 1UL, United Kingdom
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16
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Kemp MT, Lewandowski EM, Chen Y. Low barrier hydrogen bonds in protein structure and function. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2021; 1869:140557. [PMID: 33148530 PMCID: PMC7736181 DOI: 10.1016/j.bbapap.2020.140557] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 10/17/2020] [Accepted: 10/22/2020] [Indexed: 01/05/2023]
Abstract
Low-barrier hydrogen bonds (LBHBs) are a special type of short hydrogen bond (HB) that is characterized by the equal sharing of a hydrogen atom. The existence and catalytic role of LBHBs in proteins has been intensely contested. Advancements in X-ray and neutron diffraction methods has revealed delocalized hydrogen atoms involved in potential LBHBs in a number of proteins, while also demonstrating that short HBs are not necessarily LBHBs. More importantly, a series of experiments on ketosteroid isomerase (KSI) have suggested that LBHBs are significantly stronger than standard HBs in the protein microenvironment in terms of enthalpy, but not free energy. The discrepancy between the enthalpy and free energy of LBHBs offers clues to the challenges, and potential solutions, of the LBHB debate, where the unique strength of LBHBs plays a special role in the kinetic processes of enzyme function and structure, together with other molecular forces in a pre-organized environment.
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Affiliation(s)
- M Trent Kemp
- Department of Molecular Medicine, University of South Florida Morsani College of Medicine, 12901 Bruce B. Downs Blvd, MDC 3522, Tampa, Florida 33612, United States
| | - Eric M Lewandowski
- Department of Molecular Medicine, University of South Florida Morsani College of Medicine, 12901 Bruce B. Downs Blvd, MDC 3522, Tampa, Florida 33612, United States
| | - Yu Chen
- Department of Molecular Medicine, University of South Florida Morsani College of Medicine, 12901 Bruce B. Downs Blvd, MDC 3522, Tampa, Florida 33612, United States.
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17
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Stachowski TR, Snell ME, Snell EH. SAXS studies of X-ray induced disulfide bond damage: Engineering high-resolution insight from a low-resolution technique. PLoS One 2020; 15:e0239702. [PMID: 33201877 PMCID: PMC7671560 DOI: 10.1371/journal.pone.0239702] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 09/12/2020] [Indexed: 12/17/2022] Open
Abstract
A significant problem in biological X-ray crystallography is the radiation chemistry caused by the incident X-ray beam. This produces both global and site-specific damage. Site specific damage can misdirect the biological interpretation of the structural models produced. Cryo-cooling crystals has been successful in mitigating damage but not eliminating it altogether; however, cryo-cooling can be difficult in some cases and has also been shown to limit functionally relevant protein conformations. The doses used for X-ray crystallography are typically in the kilo-gray to mega-gray range. While disulfide bonds are among the most significantly affected species in proteins in the crystalline state at both cryogenic and higher temperatures, there is limited information on their response to low X-ray doses in solution, the details of which might inform biomedical applications of X-rays. In this work we engineered a protein that dimerizes through a susceptible disulfide bond to relate the radiation damage processes seen in cryo-cooled crystals to those closer to physiologic conditions. This approach enables a low-resolution technique, small angle X-ray scattering (SAXS), to detect and monitor a residue specific process. A dose dependent fragmentation of the engineered protein was seen that can be explained by a dimer to monomer transition through disulfide bond cleavage. This supports the crystallographically derived mechanism and demonstrates that results obtained crystallographically can be usefully extrapolated to physiologic conditions. Fragmentation was influenced by pH and the conformation of the dimer, providing information on mechanism and pointing to future routes for investigation and potential mitigation. The novel engineered protein approach to generate a large-scale change through a site-specific interaction represents a promising tool for advancing radiation damage studies under solution conditions.
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Affiliation(s)
- Timothy R. Stachowski
- Hauptman-Woodward Medical Research Institute, Buffalo, New York, United States of America
- Department of Cell Stress Biology, Roswell Park Comprehensive Cancer Center, Buffalo, New York, United States of America
| | - Mary E. Snell
- Hauptman-Woodward Medical Research Institute, Buffalo, New York, United States of America
| | - Edward H. Snell
- Hauptman-Woodward Medical Research Institute, Buffalo, New York, United States of America
- Department of Materials Design and Innovation, State University at New York at Buffalo, Buffalo, New York, United States of America
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18
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Kim M, Sisco NJ, Hilton JK, Montano CM, Castro MA, Cherry BR, Levitus M, Van Horn WD. Evidence that the TRPV1 S1-S4 membrane domain contributes to thermosensing. Nat Commun 2020; 11:4169. [PMID: 32820172 PMCID: PMC7441067 DOI: 10.1038/s41467-020-18026-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 07/30/2020] [Indexed: 01/14/2023] Open
Abstract
Sensing and responding to temperature is crucial in biology. The TRPV1 ion channel is a well-studied heat-sensing receptor that is also activated by vanilloid compounds, including capsaicin. Despite significant interest, the molecular underpinnings of thermosensing have remained elusive. The TRPV1 S1-S4 membrane domain couples chemical ligand binding to the pore domain during channel gating. Here we show that the S1-S4 domain also significantly contributes to thermosensing and couples to heat-activated gating. Evaluation of the isolated human TRPV1 S1-S4 domain by solution NMR, far-UV CD, and intrinsic fluorescence shows that this domain undergoes a non-denaturing temperature-dependent transition with a high thermosensitivity. Further NMR characterization of the temperature-dependent conformational changes suggests the contribution of the S1-S4 domain to thermosensing shares features with known coupling mechanisms between this domain with ligand and pH activation. Taken together, this study shows that the TRPV1 S1-S4 domain contributes to TRPV1 temperature-dependent activation.
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Affiliation(s)
- Minjoo Kim
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Nicholas J Sisco
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Jacob K Hilton
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Camila M Montano
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Manuel A Castro
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
| | - Brian R Cherry
- The Magnetic Resonance Research Center, Arizona State University, Tempe, AZ, 85287, USA
| | - Marcia Levitus
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Center for Single Molecule Biophysics, Arizona State University, Tempe, AZ, 85287, USA
| | - Wade D Van Horn
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA.
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA.
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19
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Harrison K, Wu Z, Juers DH. A comparison of gas stream cooling and plunge cooling of macromolecular crystals. J Appl Crystallogr 2019; 52:1222-1232. [PMID: 31636524 PMCID: PMC6782077 DOI: 10.1107/s1600576719010318] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 07/18/2019] [Indexed: 01/17/2023] Open
Abstract
Cryocooling for macromolecular crystallography is usually performed via plunging the crystal into a liquid cryogen or placing the crystal in a cold gas stream. These two approaches are compared here for the case of nitro-gen cooling. The results show that gas stream cooling, which typically cools the crystal more slowly, yields lower mosaicity and, in some cases, a stronger anomalous signal relative to rapid plunge cooling. During plunging, moving the crystal slowly through the cold gas layer above the liquid surface can produce mosaicity similar to gas stream cooling. Annealing plunge cooled crystals by warming and recooling in the gas stream allows the mosaicity and anomalous signal to recover. For tetragonal thermolysin, the observed effects are less pronounced when the cryosolvent has smaller thermal contraction, under which conditions the protein structures from plunge cooled and gas stream cooled crystals are very similar. Finally, this work also demonstrates that the resolution dependence of the reflecting range is correlated with the cooling method, suggesting it may be a useful tool for discerning whether crystals are cooled too rapidly. The results support previous studies suggesting that slower cooling methods are less deleterious to crystal order, as long as ice formation is prevented and dehydration is limited.
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Affiliation(s)
- Kaitlin Harrison
- Department of Physics and Program in Biochemistry, Biophysics and Molecular Biology, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
| | - Zhenguo Wu
- Department of Physics and Program in Biochemistry, Biophysics and Molecular Biology, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
| | - Douglas H Juers
- Department of Physics and Program in Biochemistry, Biophysics and Molecular Biology, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
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20
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Abstract
Denaturants such as the guanidinium cation unfold proteins at molar concentrations, which interferes with ultraviolet- and infrared-based spectroscopy measurements. Dodine denatures some proteins cooperatively at a thousand-fold lower concentration, allowing for spectroscopy measurements. Nonetheless, dodine's microscopic mechanism of interaction with proteins is not understood. We probe the effect of dodine on α-helices and tertiary structure by investigating the stability of the small helical protein B. Experiments show that dodine promotes formation of helical structure (a kosmotropic effect), while inducing the loss of tertiary structure (a chaotropic effect). Although dodine destabilizes native protein structure, it does not lower the thermal denaturation midpoint temperature of protein B. All-atom simulations reveal the cause for both observations: The denaturant action of dodine's guanidyl headgroup is counteracted by its aliphatic tail, which stabilizes amphipathic helices and associates with an expanded protein core. The Janus-like behavior of headgroup and tail make dodine a simultaneous stabilizer-destabilizer or "kosmo-chaotrope".
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Affiliation(s)
- Drishti Guin
- Department of Chemistry, University of Illinois, Urbana, IL 61801
| | - Shriyaa Mittal
- Center for Biophysics and Quantitative Biology, University of Illinois, Urbana, IL 61801
| | - Brian Bozymski
- Department of Physics, University of Illinois, Urbana, Illinois 61801
| | - Diwakar Shukla
- Center for Biophysics and Quantitative Biology, University of Illinois, Urbana, IL 61801
- Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illinois 61801
| | - Martin Gruebele
- Department of Chemistry, University of Illinois, Urbana, IL 61801
- Center for Biophysics and Quantitative Biology, University of Illinois, Urbana, IL 61801
- Department of Physics, University of Illinois, Urbana, Illinois 61801
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21
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Moreau DW, Atakisi H, Thorne RE. Ice formation and solvent nanoconfinement in protein crystals. IUCRJ 2019; 6:346-356. [PMID: 31098016 PMCID: PMC6503922 DOI: 10.1107/s2052252519001878] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 01/31/2019] [Indexed: 05/06/2023]
Abstract
Ice formation within protein crystals is a major obstacle to the cryocrystallographic study of protein structure, and has limited studies of how the structural ensemble of a protein evolves with temperature in the biophysically interesting range from ∼260 K to the protein-solvent glass transition near 200 K. Using protein crystals with solvent cavities as large as ∼70 Å, time-resolved X-ray diffraction was used to study the response of protein and internal solvent during rapid cooling. Solvent nanoconfinement suppresses freezing temperatures and ice-nucleation rates so that ice-free, low-mosaicity diffraction data can be reliably collected down to 200 K without the use of cryoprotectants. Hexagonal ice (Ih) forms in external solvent, but internal crystal solvent forms stacking-disordered ice (Isd) with a near-random stacking of cubic and hexagonal planes. Analysis of powder diffraction from internal ice and single-crystal diffraction from the host protein structure shows that the maximum crystallizable solvent fraction decreases with decreasing crystal solvent-cavity size, and that an ∼6 Å thick layer of solvent adjacent to the protein surface cannot crystallize. These results establish protein crystals as excellent model systems for the study of nanoconfined solvent. By combining fast cooling, intense X-ray beams and fast X-ray detectors, complete structural data sets for high-value targets, including membrane proteins and large complexes, may be collected at ∼220-240 K that have much lower mosaicities and comparable B factors, and that may allow more confident identification of ligand binding than in current cryocrystallographic practice.
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Affiliation(s)
- David W. Moreau
- Physics Department, Cornell University, Ithaca, NY 14853, USA
| | - Hakan Atakisi
- Physics Department, Cornell University, Ithaca, NY 14853, USA
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22
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Palese LL. Cytochrome c oxidase structures suggest a four-state stochastic pump mechanism. Phys Chem Chem Phys 2019; 21:4822-4830. [DOI: 10.1039/c8cp07365a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A simple stochastic model for a cytochrome c oxidase proton pump.
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Affiliation(s)
- Luigi Leonardo Palese
- University of Bari “Aldo Moro”
- Department of Basic Medical Sciences
- Neurosciences and Sense Organs (SMBNOS)
- Bari
- Italy
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23
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Chalikian TV, Macgregor RB. On empirical decomposition of volumetric data. Biophys Chem 2018; 246:8-15. [PMID: 30597448 DOI: 10.1016/j.bpc.2018.12.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 12/20/2018] [Accepted: 12/21/2018] [Indexed: 11/26/2022]
Abstract
Volumetric characterization of proteins and their recognition events has been instrumental in providing information on the role of intra- and intermolecular interactions, including hydration, in stabilizing biomolecules. The credibility of molecular models and interpretation schemes used to rationalize experimental data are essential for the validity of microscopic insights derived from volumetric results. Current empirical schemes used to interpret volumetric data suffer from a lack of theoretical and computational substantiation. In this contribution, we take advantage age of recent MD simulations of proteins in solution coupled with Voronoi-Delaunay tessellation of simulated structures that have provided an exceptional level of structural detail on the nature of protein-water interfaces. We use these structural insights to re-evaluate empirical frameworks used for interpretation of volumetric data. An important issue in this respect is the actual dividing surface between water and protein atoms that is used in volumetric studies when the solute and solvent are treated as hard spheres enclosed within their respective van der Waals surfaces. In one development, using Voronoi tessellation of MD simulated protein-water systems the dividing surface has been defined as the points equidistant from the water and protein atoms. The interstitial void volume between the solute and the dividing surface corresponds to thermal volume envisaged by Scaled Particle Theory. In this communication, we explicitly account for the contributions of thermal volume to the partial molar volume, compressibility, and expansibility of proteins and re-examine and redefine the intrinsic and hydration volumetric contributions. We discuss the implications of our results for protein transitions and association events.
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Affiliation(s)
- Tigran V Chalikian
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada.
| | - Robert B Macgregor
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada
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24
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Juers DH, Farley CA, Saxby CP, Cotter RA, Cahn JKB, Holton-Burke RC, Harrison K, Wu Z. The impact of cryosolution thermal contraction on proteins and protein crystals: volumes, conformation and order. Acta Crystallogr D Struct Biol 2018; 74:922-938. [PMID: 30198901 PMCID: PMC6130464 DOI: 10.1107/s2059798318008793] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 06/15/2018] [Indexed: 11/11/2022] Open
Abstract
Cryocooling of macromolecular crystals is commonly employed to limit radiation damage during X-ray diffraction data collection. However, cooling itself affects macromolecular conformation and often damages crystals via poorly understood processes. Here, the effects of cryosolution thermal contraction on macromolecular conformation and crystal order in crystals ranging from 32 to 67% solvent content are systematically investigated. It is found that the solution thermal contraction affects macromolecule configurations and volumes, unit-cell volumes, crystal packing and crystal order. The effects occur through not only thermal contraction, but also pressure caused by the mismatched contraction of cryosolvent and pores. Higher solvent-content crystals are more affected. In some cases the solvent contraction can be adjusted to reduce mosaicity and increase the strength of diffraction. Ice formation in some crystals is found to cause damage via a reduction in unit-cell volume, which is interpreted through solvent transport out of unit cells during cooling. The results point to more deductive approaches to cryoprotection optimization by adjusting the cryosolution composition to reduce thermal contraction-induced stresses in the crystal with cooling.
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Affiliation(s)
- Douglas H. Juers
- Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
- Program in BBMB, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
| | - Christopher A. Farley
- Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
| | | | - Rosemary A. Cotter
- Program in BBMB, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
| | - Jackson K. B. Cahn
- Program in BBMB, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
| | | | - Kaitlin Harrison
- Program in BBMB, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
| | - Zhenguo Wu
- Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362, USA
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25
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Carugo O. Atomic displacement parameters in structural biology. Amino Acids 2018; 50:775-786. [DOI: 10.1007/s00726-018-2574-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/19/2018] [Indexed: 01/14/2023]
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26
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Chen T, Dave K, Gruebele M. Pressure- and heat-induced protein unfolding in bacterial cells: crowding vs. sticking. FEBS Lett 2018. [PMID: 29520756 DOI: 10.1002/1873-3468.13025] [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] [Indexed: 11/11/2022]
Abstract
In-cell protein stability is increased by crowding, but can be reduced by destabilizing surface interactions. Will different denaturation techniques yield similar trends? Here, we apply pressure and thermal denaturation to green fluorescent protein/ReAsH-labeled yeast phosphoglycerate kinase (PGK) in Escherichia coli cells. Pressure denaturation is more two state-like in E. coli than in vitro, stabilizing the native state. Thermal denaturation destabilizes PGK in E. coli, unlike in mammalian cells. Results in wild-type MG1655 strain are corroborated in pressure-resistant J1 strain, where PGK is less prone to aggregation. Thus, destabilizing surface interactions overcome stabilizing crowding in the E. coli cytoplasm under thermal denaturation, but not under pressure denaturation.
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Affiliation(s)
- Timothy Chen
- Department of Chemistry, University of Illinois, Urbana, IL, USA
| | - Kapil Dave
- Center for Biophysics and Quantitative Biology, University of Illinois, Urbana, IL, USA
| | - Martin Gruebele
- Department of Chemistry, University of Illinois, Urbana, IL, USA.,Center for Biophysics and Quantitative Biology, University of Illinois, Urbana, IL, USA.,Department of Physics, University of Illinois, Urbana, IL, USA
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27
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Grille Coronel L, Acierno JP, Ermácora MR. Ultracompact states of native proteins. Biophys Chem 2017; 230:36-44. [DOI: 10.1016/j.bpc.2017.08.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 08/16/2017] [Indexed: 10/19/2022]
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28
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Naitow H, Matsuura Y, Tono K, Joti Y, Kameshima T, Hatsui T, Yabashi M, Tanaka R, Tanaka T, Sugahara M, Kobayashi J, Nango E, Iwata S, Kunishima N. Protein-ligand complex structure from serial femtosecond crystallography using soaked thermolysin microcrystals and comparison with structures from synchrotron radiation. Acta Crystallogr D Struct Biol 2017; 73:702-709. [PMID: 28777085 PMCID: PMC5571745 DOI: 10.1107/s2059798317008919] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 06/14/2017] [Indexed: 01/09/2023] Open
Abstract
Serial femtosecond crystallography (SFX) with an X-ray free-electron laser is used for the structural determination of proteins from a large number of microcrystals at room temperature. To examine the feasibility of pharmaceutical applications of SFX, a ligand-soaking experiment using thermolysin microcrystals has been performed using SFX. The results were compared with those from a conventional experiment with synchrotron radiation (SR) at 100 K. A protein-ligand complex structure was successfully obtained from an SFX experiment using microcrystals soaked with a small-molecule ligand; both oil-based and water-based crystal carriers gave essentially the same results. In a comparison of the SFX and SR structures, clear differences were observed in the unit-cell parameters, in the alternate conformation of side chains, in the degree of water coordination and in the ligand-binding mode.
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Affiliation(s)
- Hisashi Naitow
- Bio-Specimen Platform Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Yoshinori Matsuura
- Bio-Specimen Platform Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Kensuke Tono
- XFEL Research and Development Division, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Yasumasa Joti
- XFEL Research and Development Division, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Takashi Kameshima
- XFEL Research and Development Division, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Takaki Hatsui
- XFEL Research and Development Division, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Makina Yabashi
- XFEL Research and Development Division, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Rie Tanaka
- SACLA Science Research Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Tomoyuki Tanaka
- SACLA Science Research Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Michihiro Sugahara
- SACLA Science Research Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Jun Kobayashi
- SACLA Science Research Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Eriko Nango
- SACLA Science Research Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - So Iwata
- SACLA Science Research Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Naoki Kunishima
- Bio-Specimen Platform Group, RIKEN SPring-8 Center, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
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29
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Law AB, Sapienza PJ, Zhang J, Zuo X, Petit CM. Native State Volume Fluctuations in Proteins as a Mechanism for Dynamic Allostery. J Am Chem Soc 2017; 139:3599-3602. [PMID: 28094513 DOI: 10.1021/jacs.6b12058] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Allostery enables tight regulation of protein function in the cellular environment. Although existing models of allostery are firmly rooted in the current structure-function paradigm, the mechanistic basis for allostery in the absence of structural change remains unclear. In this study, we show that a typical globular protein is able to undergo significant changes in volume under native conditions while exhibiting no additional changes in protein structure. These native state volume fluctuations were found to correlate with changes in internal motions that were previously recognized as a source of allosteric entropy. This finding offers a novel mechanistic basis for allostery in the absence of canonical structural change. The unexpected observation that function can be derived from expanded, low density protein states has broad implications for our understanding of allostery and suggests that the general concept of the native state be expanded to allow for more variable physical dimensions with looser packing.
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Affiliation(s)
- Anthony B Law
- Department of Otolaryngology - Head and Neck Surgery, University of Washington , Seattle, Washington 98195, United States
| | - Paul J Sapienza
- Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
| | - Jun Zhang
- Department of Chemistry, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
| | - Xiaobing Zuo
- X-ray Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Chad M Petit
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
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30
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When proteins are completely hydrated in crystals. Int J Biol Macromol 2016; 89:137-43. [DOI: 10.1016/j.ijbiomac.2016.04.061] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/15/2016] [Accepted: 04/21/2016] [Indexed: 12/16/2022]
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31
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Khanal D, Kondyurin A, Hau H, Knowles JC, Levinson O, Ramzan I, Fu D, Marcott C, Chrzanowski W. Biospectroscopy of Nanodiamond-Induced Alterations in Conformation of Intra- and Extracellular Proteins: A Nanoscale IR Study. Anal Chem 2016; 88:7530-8. [DOI: 10.1021/acs.analchem.6b00665] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Dipesh Khanal
- Faculty
of Pharmacy, The University of Sydney, NSW 2006, Australia
| | - Alexey Kondyurin
- School
of Physics, The University of Sydney, NSW 2006, Australia
| | - Herman Hau
- Faculty
of Pharmacy, The University of Sydney, NSW 2006, Australia
| | - Jonathan C. Knowles
- Division
of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, University College London, 256 Gray’s Inn Road, London WC1X 8LD, U.K
| | | | - Iqbal Ramzan
- Faculty
of Pharmacy, The University of Sydney, NSW 2006, Australia
| | - Dong Fu
- Faculty
of Pharmacy, The University of Sydney, NSW 2006, Australia
| | - Curtis Marcott
- Light Light Solutions, P.O. Box 81486, Athens, Georgia 30608-1484, United States
| | - Wojciech Chrzanowski
- Faculty
of Pharmacy, The University of Sydney, NSW 2006, Australia
- Australian
Institute of Nanoscale Science and Technology, The University of Sydney, NSW 2006, Australia
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32
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Roedig P, Duman R, Sanchez-Weatherby J, Vartiainen I, Burkhardt A, Warmer M, David C, Wagner A, Meents A. Room-temperature macromolecular crystallography using a micro-patterned silicon chip with minimal background scattering. J Appl Crystallogr 2016; 49:968-975. [PMID: 27275143 PMCID: PMC4886986 DOI: 10.1107/s1600576716006348] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 04/14/2016] [Indexed: 11/25/2022] Open
Abstract
Recent success at X-ray free-electron lasers has led to serial crystallography experiments staging a comeback at synchrotron sources as well. With crystal lifetimes typically in the millisecond range and the latest-generation detector technologies with high framing rates up to 1 kHz, fast sample exchange has become the bottleneck for such experiments. A micro-patterned chip has been developed from single-crystalline silicon, which acts as a sample holder for up to several thousand microcrystals at a very low background level. The crystals can be easily loaded onto the chip and excess mother liquor can be efficiently removed. Dehydration of the crystals is prevented by keeping them in a stream of humidified air during data collection. Further sealing of the sample holder, for example with Kapton, is not required. Room-temperature data collection from insulin crystals loaded onto the chip proves the applicability of the chip for macromolecular crystallography. Subsequent structure refinements reveal no radiation-damage-induced structural changes for insulin crystals up to a dose of 565.6 kGy, even though the total diffraction power of the crystals has on average decreased to 19.1% of its initial value for the same dose. A decay of the diffracting power by half is observed for a dose of D1/2 = 147.5 ± 19.1 kGy, which is about 1/300 of the dose before crystals show a similar decay at cryogenic temperatures.
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Affiliation(s)
- Philip Roedig
- Deutsches Elektronen-Synchrotron DESY, Photon Science, Notkestrasse 85, Hamburg 22607, Germany
| | - Ramona Duman
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Juan Sanchez-Weatherby
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
| | | | - Anja Burkhardt
- Deutsches Elektronen-Synchrotron DESY, Photon Science, Notkestrasse 85, Hamburg 22607, Germany
| | - Martin Warmer
- Deutsches Elektronen-Synchrotron DESY, Photon Science, Notkestrasse 85, Hamburg 22607, Germany
| | | | - Armin Wagner
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Alke Meents
- Deutsches Elektronen-Synchrotron DESY, Photon Science, Notkestrasse 85, Hamburg 22607, Germany
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33
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Ortore MG, Macedo JNA, Araujo APU, Ferrero C, Mariani P, Spinozzi F, Itri R. Structural and Thermodynamic Properties of Septin 3 Investigated by Small-Angle X-Ray Scattering. Biophys J 2016; 108:2896-902. [PMID: 26083929 DOI: 10.1016/j.bpj.2015.05.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 04/30/2015] [Accepted: 05/11/2015] [Indexed: 01/22/2023] Open
Abstract
Septins comprise a family of proteins involved in a variety of cellular processes and related to several human pathologies. They are constituted by three structural domains: the N- and C-terminal domains, highly variable in length and composition, and the central domain, involved in the guanine nucleotide (GTP) binding. Thirteen different human septins are known to form heterogeneous complexes or homofilaments, which are stabilized by specific interactions between the different interfaces present in the domains. In this work, we have investigated by in-solution small-angle x-ray scattering the structural and thermodynamic properties of a human septin 3 construct, SEPT3-GC, which contains both of both interfaces (G and NC) responsible for septin-septin interactions. In order to shed light on the role of these interactions, small-angle x-ray scattering measurements were performed in a wide range of temperatures, from 2 up to 56°C, both with and without a nonhydrolysable form of GTP (GTPγS). The acquired data show a temperature-dependent coexistence of monomers, dimers, and higher-order aggregates that were analyzed using a global fitting approach, taking into account the crystallographic structure of the recently reported SEPT3 dimer, PDB:3SOP. As a result, the enthalpy, entropy, and heat capacity variations that control the dimer-monomer dissociation equilibrium in solution were derived and GTPγS was detected to increase the enthalpic stability of the dimeric species. Moreover, a temperature increase was observed to induce dissociation of SEPT3-GC dimers into monomers just preceding their reassembling into amyloid aggregates, as revealed by the Thioflavin-T fluorescence assays.
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Affiliation(s)
- Maria Grazia Ortore
- Dipartimento di Scienze della Vita e dell'Ambiente and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Università Politecnica delle Marche, Ancona, Italy
| | - Joci N A Macedo
- Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil
| | - Ana Paula U Araujo
- Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil
| | | | - Paolo Mariani
- Dipartimento di Scienze della Vita e dell'Ambiente and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Università Politecnica delle Marche, Ancona, Italy
| | - Francesco Spinozzi
- Dipartimento di Scienze della Vita e dell'Ambiente and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Università Politecnica delle Marche, Ancona, Italy.
| | - Rosangela Itri
- Instituto de Física da Universidade de São Paulo, São Paulo, Brazil.
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34
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Sundby S, Kristiansen T. The Principles of Buoyancy in Marine Fish Eggs and Their Vertical Distributions across the World Oceans. PLoS One 2015; 10:e0138821. [PMID: 26465149 PMCID: PMC4605736 DOI: 10.1371/journal.pone.0138821] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 09/03/2015] [Indexed: 11/22/2022] Open
Abstract
Buoyancy acting on plankton, i.e. the difference in specific gravity between plankton and the ambient water, is a function of salinity and temperature. From specific gravity measurements of marine fish eggs salinity appears to be the only determinant of the buoyancy indicating that the thermal expansions of the fish egg and the ambient seawater are equal. We analyze the mechanisms behind thermal expansion in fish eggs in order to determine to what extent it can be justified to neglect the effects of temperature on buoyancy. Our results confirm the earlier assumptions that salinity is the basic determinant on buoyancy in marine fish eggs that, in turn, influence the vertical distributions and, consequently, the dispersal of fish eggs from the spawning areas. Fish populations have adapted accordingly by producing egg specific gravities that tune the egg buoyancy to create specific vertical distributions for each local population. A wide variety of buoyancy adaptations are found among fish populations. The ambient physical conditions at the spawning sites form a basic constraint for adaptation. In coastal regions where salinity increases with depth, and where the major fraction of the fish stocks spawns, pelagic and mesopelagic egg distributions dominate. However, in the larger part of worlds’ oceans salinity decreases with depth resulting in different egg distributions. Here, the principles of vertical distributions of fish eggs in the world oceans are presented in an overarching framework presenting the basic differences between regions, mainly coastal, where salinity increases with depth and the major part of the world oceans where salinity decreases with depth. We show that under these latter conditions, steady-state vertical distribution of mesopelagic fish eggs cannot exist as it does in most coastal regions. In fact, a critical spawning depth must exist where spawning below this depth threshold results in eggs sinking out of the water column and become lost for recruitment to the population. An example of adaptation to such conditions is Cape hake spawning above the critical layer in the Northern Benguela upwelling ecosystem. The eggs rise slowly in the onshore subsurface current below the Ekman layer, hence being advected inshore where the hatched larvae concentrate with optimal feeding conditions.
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Affiliation(s)
- Svein Sundby
- Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics, P.O. Box 1870 Nordnes, 5817, Bergen, Norway
| | - Trond Kristiansen
- Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics, P.O. Box 1870 Nordnes, 5817, Bergen, Norway
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35
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Keedy DA, Kenner LR, Warkentin M, Woldeyes RA, Hopkins JB, Thompson MC, Brewster AS, Van Benschoten AH, Baxter EL, Uervirojnangkoorn M, McPhillips SE, Song J, Alonso-Mori R, Holton JM, Weis WI, Brunger AT, Soltis SM, Lemke H, Gonzalez A, Sauter NK, Cohen AE, van den Bedem H, Thorne RE, Fraser JS. Mapping the conformational landscape of a dynamic enzyme by multitemperature and XFEL crystallography. eLife 2015; 4. [PMID: 26422513 PMCID: PMC4721965 DOI: 10.7554/elife.07574] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 09/29/2015] [Indexed: 12/14/2022] Open
Abstract
Determining the interconverting conformations of dynamic proteins in atomic detail is a major challenge for structural biology. Conformational heterogeneity in the active site of the dynamic enzyme cyclophilin A (CypA) has been previously linked to its catalytic function, but the extent to which the different conformations of these residues are correlated is unclear. Here we compare the conformational ensembles of CypA by multitemperature synchrotron crystallography and fixed-target X-ray free-electron laser (XFEL) crystallography. The diffraction-before-destruction nature of XFEL experiments provides a radiation-damage-free view of the functionally important alternative conformations of CypA, confirming earlier synchrotron-based results. We monitored the temperature dependences of these alternative conformations with eight synchrotron datasets spanning 100-310 K. Multiconformer models show that many alternative conformations in CypA are populated only at 240 K and above, yet others remain populated or become populated at 180 K and below. These results point to a complex evolution of conformational heterogeneity between 180-–240 K that involves both thermal deactivation and solvent-driven arrest of protein motions in the crystal. The lack of a single shared conformational response to temperature within the dynamic active-site network provides evidence for a conformation shuffling model, in which exchange between rotamer states of a large aromatic ring in the middle of the network shifts the conformational ensemble for the other residues in the network. Together, our multitemperature analyses and XFEL data motivate a new generation of temperature- and time-resolved experiments to structurally characterize the dynamic underpinnings of protein function. DOI:http://dx.doi.org/10.7554/eLife.07574.001 Proteins are the workhorses of the cell. The shape that a protein molecule adopts enables it to carry out its role. However, a protein’s shape, or 'conformation', is not static. Instead, a protein can shift between different conformations. This is particularly true for enzymes – the proteins that catalyze chemical reactions. The region of an enzyme where the chemical reaction happens, known as the active site, often has to change its conformation to allow catalysis to proceed. Changes in temperature can also make a protein shift between alternative conformations. Understanding how a protein shifts between conformations gives insight into how it works. A common method for studying protein conformation is X-ray crystallography. This technique uses a beam of X-rays to figure out where the atoms of the protein are inside a crystal made of millions of copies of that protein. At room temperature or biological temperature, X-rays can rapidly damage the protein. Because of this, most crystal structures are determined at very low temperatures to minimize damage. But cooling to low temperatures changes the conformations that the protein adopts, and usually causes fewer conformations to be present. Keedy, Kenner, Warkentin, Woldeyes et al. have used X-ray crystallography from a very low temperature (-173°C or 100 K) to above room temperature (up to 27°C or 300 K) to explore the alternative conformations of an enzyme called cyclophilin A. These alternative conformations include those that have previously been linked to this enzyme’s activity. Starting at a low temperature, parts of the enzyme were seen to shift from having a single conformation to many conformations above a threshold temperature. Unexpectedly, different parts of the enzyme have different threshold temperatures, suggesting that there isn’t a single transition across the whole protein. Instead, it appears the way a protein’s conformation changes in response to temperature is more complex than was previously realized. This result suggests that conformations in different parts of a protein are coupled to each other in complex ways. Keedy, Kenner, Warkentin, Woldeyes et al. then performed X-ray crystallography at room temperature using an X-ray free-electron laser (XFEL). This technique can capture the protein’s structure before radiation damage occurs, and confirmed that the alternative conformations observed were not affected by radiation damage. The combination of X-ray crystallography at multiple temperatures, new analysis methods for identifying and measuring alternative conformations, and XFEL crystallography should help future studies to characterize conformational changes in other proteins. DOI:http://dx.doi.org/10.7554/eLife.07574.002
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Affiliation(s)
- Daniel A Keedy
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, United States
| | - Lillian R Kenner
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, United States
| | | | - Rahel A Woldeyes
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, United States
| | - Jesse B Hopkins
- Department of Physics, Cornell University, Ithaca, United States
| | - Michael C Thompson
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, United States
| | - Aaron S Brewster
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Andrew H Van Benschoten
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, United States
| | - Elizabeth L Baxter
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Monarin Uervirojnangkoorn
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States.,Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Scott E McPhillips
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Jinhu Song
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - James M Holton
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States.,Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - William I Weis
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States.,Department of Structural Biology, Stanford University, Stanford, United States.,Department of Photon Science, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States.,Howard Hughes Medical Institute, Stanford University, Stanford, United States.,Department of Structural Biology, Stanford University, Stanford, United States.,Department of Photon Science, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - S Michael Soltis
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Henrik Lemke
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Ana Gonzalez
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Nicholas K Sauter
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Aina E Cohen
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Henry van den Bedem
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Robert E Thorne
- Department of Physics, Cornell University, Ithaca, United States
| | - James S Fraser
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, United States
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36
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High-Pressure EPR and Site-Directed Spin Labeling for Mapping Molecular Flexibility in Proteins. Methods Enzymol 2015; 564:29-57. [PMID: 26477247 DOI: 10.1016/bs.mie.2015.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
High hydrostatic pressure is a powerful probe of protein conformational flexibility. Pressurization reveals regions of elevated compressibility, and thus flexibility, within individual conformational states, but also shifts conformational equilibria such that "invisible" excited states become accessible for spectroscopic characterization. The central aim of this chapter is to describe recently developed instrumentation and methodologies that enable high-pressure site-directed spin labeling electron paramagnetic resonance (SDSL-EPR) experiments on proteins and to demonstrate the information content of these experiments by highlighting specific recent applications. A brief introduction to the thermodynamics of proteins under pressure is presented first, followed by a discussion of the principles underlying SDSL-EPR detection of pressure effects in proteins, and the suitability of SDSL-EPR for this purpose in terms of timescale and ability to characterize conformational heterogeneity. Instrumentation and practical considerations for variable-pressure continuous wave EPR and pressure-resolved double electron-electron resonance (PR DEER) experiments are reviewed, and finally illustrations of data analysis using recent applications are presented. Although high-pressure SDSL-EPR is in its infancy, the recent applications presented highlight the considerable potential of the method to (1) identify compressible (flexible) regions in a folded protein; (2) determine thermodynamic parameters that relate conformational states in equilibrium; (3) populate and characterize excited states of proteins undetected at atmospheric pressure; (4) reveal the structural heterogeneity of conformational ensembles and provide distance constraints on the global structure of pressure-populated states with PR DEER.
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37
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Abstract
The partial specific (or molar) volume, expansibility, and compressibility of a protein are fundamental thermodynamic quantities for characterizing its structure in solution. We review the definitions, measurements, and implications of these volumetric quantities in relation to protein structural biology. The partial specific volumes under constant molality (isomolal) and chemical potential (isopotential) conditions of the cosolvent (multicomponent systems) are explained in terms of preferential solvent interactions relevant to the solubility and stability of proteins. The partial expansibility is briefly discussed in terms of the effects of temperature on protein-solvent interactions (hydration) and internal packing defects (cavities). We discuss the compressibility-structure-function relationships of proteins based on analyses of the correlations between the partial adiabatic compressibilities and the structures or functions of various globular proteins (including mutants), focusing on the roles of the internal cavities in structural fluctuations. The volume and compressibility changes associated with various conformational transitions are also discussed in terms of the changes in hydration and cavities in order to elucidate the nonnative structures and the transition mechanisms, especially those associated with pressure denaturation.
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38
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E pluribus unum, no more: from one crystal, many conformations. Curr Opin Struct Biol 2014; 28:56-62. [PMID: 25113271 DOI: 10.1016/j.sbi.2014.07.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 07/10/2014] [Accepted: 07/18/2014] [Indexed: 11/22/2022]
Abstract
Several distinct computational approaches have recently been implemented to represent conformational heterogeneity from X-ray crystallography datasets that are averaged in time and space. As these modeling methods mature, newly discovered alternative conformations are being used to derive functional protein mechanisms. Room temperature X-ray data collection is emerging as a key variable for sampling functionally relevant conformations also observed in solution studies. Although concerns about radiation damage are warranted with higher temperature data collection, 'diffract and destroy' strategies on X-ray free electron lasers may permit radiation damage-free data collection. X-ray crystallography need not be confined to 'static unique snapshots'; these experimental and computational advances are revealing how the many conformations populated within a single crystal are used in biological mechanisms.
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39
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Keedy DA, van den Bedem H, Sivak DA, Petsko GA, Ringe D, Wilson MA, Fraser JS. Crystal cryocooling distorts conformational heterogeneity in a model Michaelis complex of DHFR. Structure 2014; 22:899-910. [PMID: 24882744 DOI: 10.1016/j.str.2014.04.016] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 04/26/2014] [Accepted: 04/29/2014] [Indexed: 11/28/2022]
Abstract
Most macromolecular X-ray structures are determined from cryocooled crystals, but it is unclear whether cryocooling distorts functionally relevant flexibility. Here we compare independently acquired pairs of high-resolution data sets of a model Michaelis complex of dihydrofolate reductase (DHFR), collected by separate groups at both room and cryogenic temperatures. These data sets allow us to isolate the differences between experimental procedures and between temperatures. Our analyses of multiconformer models and time-averaged ensembles suggest that cryocooling suppresses and otherwise modifies side-chain and main-chain conformational heterogeneity, quenching dynamic contact networks. Despite some idiosyncratic differences, most changes from room temperature to cryogenic temperature are conserved and likely reflect temperature-dependent solvent remodeling. Both cryogenic data sets point to additional conformations not evident in the corresponding room temperature data sets, suggesting that cryocooling does not merely trap preexisting conformational heterogeneity. Our results demonstrate that crystal cryocooling consistently distorts the energy landscape of DHFR, a paragon for understanding functional protein dynamics.
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Affiliation(s)
- Daniel A Keedy
- Department of Bioengineering and Therapeutic Sciences and California Institute for Quantitative Biology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Henry van den Bedem
- Joint Center for Structural Genomics, Stanford Synchrotron Radiation Lightsource, Stanford, CA 94025, USA
| | - David A Sivak
- Center for Systems and Synthetic Biology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Gregory A Petsko
- Department of Biochemistry and Chemistry, Brandeis University, Waltham, MA 02454, USA; Department of Neurology and Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02139, USA
| | - Dagmar Ringe
- Department of Neurology and Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02139, USA
| | - Mark A Wilson
- Department of Biochemistry and the Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA.
| | - James S Fraser
- Department of Bioengineering and Therapeutic Sciences and California Institute for Quantitative Biology, University of California, San Francisco, San Francisco, CA 94158, USA.
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40
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Hill JJ, Shalaev EY, Zografi G. The importance of individual protein molecule dynamics in developing and assessing solid state protein preparations. J Pharm Sci 2014; 103:2605-2614. [PMID: 24867196 DOI: 10.1002/jps.24021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 11/09/2022]
Abstract
Processing protein solutions into the solid state is a common approach for generating stable amorphous protein mixtures that are suitable for long-term storage. Great care is typically given to protecting the protein native structure during the various drying steps that render it into the amorphous solid state. However, many studies illustrate that chemical and physical degradations still occur in spite of this amorphous material having good glassy properties and it being stored at temperatures below its glass transition temperature (Tg). Because of these persistent issues and recent biophysical studies that have refined the debate ascribing meaning to the molecular dynamical transition temperature and Tg of protein molecules, we provide an updated discussion on the impact of assessing and managing localized, individual protein molecule nondiffusive motions in the context of proteins being prepared into bulk amorphous mixtures. Our aim is to bridge the pharmaceutical studies addressing bulk amorphous preparations and their glassy behavior, with the biophysical studies historically focused on the nondiffusive internal protein dynamics and a protein's activity, along with their combined efforts in assessing the impact of solvent hydrogen-bonding networks on local stability. We also provide recommendations for future research efforts in solid-state formulation approaches.
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Affiliation(s)
- John J Hill
- Department of Bioengineering, University of Washington, Seattle, WA 98195.
| | | | - George Zografi
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53705-2222
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41
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Mapping protein conformational heterogeneity under pressure with site-directed spin labeling and double electron-electron resonance. Proc Natl Acad Sci U S A 2014; 111:E1201-10. [PMID: 24707053 DOI: 10.1073/pnas.1403179111] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The dominance of a single native state for most proteins under ambient conditions belies the functional importance of higher-energy conformational states (excited states), which often are too sparsely populated to allow spectroscopic investigation. Application of high hydrostatic pressure increases the population of excited states for study, but structural characterization is not trivial because of the multiplicity of states in the ensemble and rapid (microsecond to millisecond) exchange between them. Site-directed spin labeling in combination with double electron-electron resonance (DEER) provides long-range (20-80 Å) distance distributions with angstrom-level resolution and thus is ideally suited to resolve conformational heterogeneity in an excited state populated under high pressure. DEER currently is performed at cryogenic temperatures. Therefore, a method was developed for rapidly freezing spin-labeled proteins under pressure to kinetically trap the high-pressure conformational ensemble for subsequent DEER data collection at atmospheric pressure. The methodology was evaluated using seven doubly-labeled mutants of myoglobin designed to monitor selected interhelical distances. For holomyoglobin, the distance distributions are narrow and relatively insensitive to pressure. In apomyoglobin, on the other hand, the distributions reveal a striking conformational heterogeneity involving specific helices in the pressure range of 0-3 kbar, where a molten globule state is formed. The data directly reveal the amplitude of helical fluctuations, information unique to the DEER method that complements previous rate determinations. Comparison of the distance distributions for pressure- and pH-populated molten globules shows them to be remarkably similar despite a lower helical content in the latter.
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42
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Rashin AA, Domagalski MJ, Zimmermann MT, Minor W, Chruszcz M, Jernigan RL. Factors correlating with significant differences between X-ray structures of myoglobin. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:481-91. [PMID: 24531482 PMCID: PMC3940193 DOI: 10.1107/s1399004713028812] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 10/20/2013] [Indexed: 11/10/2022]
Abstract
Validation of general ideas about the origins of conformational differences in proteins is critical in order to arrive at meaningful functional insights. Here, principal component analysis (PCA) and distance difference matrices are used to validate some such ideas about the conformational differences between 291 myoglobin structures from sperm whale, horse and pig. Almost all of the horse and pig structures form compact PCA clusters with only minor coordinate differences and outliers that are easily explained. The 222 whale structures form a few dense clusters with multiple outliers. A few whale outliers with a prominent distortion of the GH loop are very similar to the cluster of horse structures, which all have a similar GH-loop distortion apparently owing to intermolecular crystal lattice hydrogen bonds to the GH loop from residues near the distal histidine His64. The variations of the GH-loop coordinates in the whale structures are likely to be owing to the observed alternative intermolecular crystal lattice bond, with the change to the GH loop distorting bonds correlated with the binding of specific `unusual' ligands. Such an alternative intermolecular bond is not observed in horse myoglobins, obliterating any correlation with the ligands. Intermolecular bonds do not usually cause significant coordinate differences and cannot be validated as their universal cause. Most of the native-like whale myoglobin structure outliers can be correlated with a few specific factors. However, these factors do not always lead to coordinate differences beyond the previously determined uncertainty thresholds. The binding of unusual ligands by myoglobin, leading to crystal-induced distortions, suggests that some of the conformational differences between the apo and holo structures might not be `functionally important' but rather artifacts caused by the binding of `unusual' substrate analogs. The causes of P6 symmetry in myoglobin crystals and the relationship between crystal and solution structures are also discussed.
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Affiliation(s)
- Alexander A. Rashin
- BioChemComp Inc., 543 Sagamore Avenue, Teaneck, NJ 07666, USA
- LH Baker Center for Bioinformatics and Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 112 Office and Lab Bldg, Ames, IA 50011-3020, USA
| | - Marcin J. Domagalski
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Jordan Hall, Room 4223, Charlottesville, VA 22908, USA
| | - Michael T. Zimmermann
- LH Baker Center for Bioinformatics and Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 112 Office and Lab Bldg, Ames, IA 50011-3020, USA
| | - Wladek Minor
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Jordan Hall, Room 4223, Charlottesville, VA 22908, USA
| | - Maksymilian Chruszcz
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Jordan Hall, Room 4223, Charlottesville, VA 22908, USA
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, SC 29208, USA
| | - Robert L. Jernigan
- LH Baker Center for Bioinformatics and Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 112 Office and Lab Bldg, Ames, IA 50011-3020, USA
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43
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Circular dichroism and site-directed spin labeling reveal structural and dynamical features of high-pressure states of myoglobin. Proc Natl Acad Sci U S A 2013; 110:E4714-22. [PMID: 24248390 DOI: 10.1073/pnas.1320124110] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Excited states of proteins may play important roles in function, yet are difficult to study spectroscopically because of their sparse population. High hydrostatic pressure increases the equilibrium population of excited states, enabling their characterization [Akasaka K (2003) Biochemistry 42:10875-85]. High-pressure site-directed spin-labeling EPR (SDSL-EPR) was developed recently to map the site-specific structure and dynamics of excited states populated by pressure. To monitor global secondary structure content by circular dichroism (CD) at high pressure, a modified optical cell using a custom MgF2 window with a reduced aperture is introduced. Here, a combination of SDSL-EPR and CD is used to map reversible structural transitions in holomyoglobin and apomyoglobin (apoMb) as a function of applied pressure up to 2 kbar. CD shows that the high-pressure excited state of apoMb at pH 6 has helical content identical to that of native apoMb, but reversible changes reflecting the appearance of a conformational ensemble are observed by SDSL-EPR, suggesting a helical topology that fluctuates slowly on the EPR time scale. Although the high-pressure state of apoMb at pH 6 has been referred to as a molten globule, the data presented here reveal significant differences from the well-characterized pH 4.1 molten globule of apoMb. Pressure-populated states of both holomyoglobin and apoMb at pH 4.1 have significantly less helical structure, and for the latter, that may correspond to a transient folding intermediate.
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44
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Garg A, Mark Manidhar D, Gokara M, Malleda C, Suresh Reddy C, Subramanyam R. Elucidation of the binding mechanism of coumarin derivatives with human serum albumin. PLoS One 2013; 8:e63805. [PMID: 23724004 PMCID: PMC3665821 DOI: 10.1371/journal.pone.0063805] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 04/05/2013] [Indexed: 11/19/2022] Open
Abstract
Coumarin is a benzopyrone which is widely used as an anti-coagulant, anti-oxidant, anti-cancer and also to cure arthritis, herpes, asthma and inflammation. Here, we studied the binding of synthesized coumarin derivatives with human serum albumin (HSA) at physiological pH 7.2 by using fluorescence spectroscopy, circular dichroism spectroscopy, molecular docking and molecular dynamics simulation studies. By addition of coumarin derivatives to HSA the maximum fluorescence intensity was reduced due to quenching of intrinsic fluorescence upon binding of coumarin derivatives to HSA. The binding constant and free energy were found to be 1.957±0.01×10(5) M(-1), -7.175 Kcal M(-1) for coumarin derivative (CD) enamide; 0.837±0.01×10(5) M(-1), -6.685 Kcal M(-1) for coumarin derivative (CD) enoate, and 0.606±0.01×10(5) M(-1), -6.49 Kcal M(-1) for coumarin derivative methylprop (CDM) enamide. The CD spectroscopy showed that the protein secondary structure was partially unfolded upon binding of coumarin derivatives. Further, the molecular docking studies showed that coumarin derivatives were binding to HSA at sub-domain IB with the hydrophobic interactions and also with hydrogen bond interactions. Additionally, the molecular dynamics simulations studies contributed in understanding the stability of protein-drug complex system in the aqueous solution and the conformational changes in HSA upon binding of coumarin derivatives. This study will provide insights into designing of the new inspired coumarin derivatives as therapeutic agents against many life threatening diseases.
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Affiliation(s)
- Archit Garg
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Darla Mark Manidhar
- Department of Chemistry, Sri Venkateswara University, Tirupathi, Andhrapradesh, India
| | - Mahesh Gokara
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Chandramouli Malleda
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Cirandur Suresh Reddy
- Department of Chemistry, Sri Venkateswara University, Tirupathi, Andhrapradesh, India
| | - Rajagopal Subramanyam
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
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45
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Tol MB, Deluz C, Hassaine G, Graff A, Stahlberg H, Vogel H. Thermal unfolding of a mammalian pentameric ligand-gated ion channel proceeds at consecutive, distinct steps. J Biol Chem 2012; 288:5756-69. [PMID: 23275379 DOI: 10.1074/jbc.m112.422287] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Pentameric ligand-gated ion channels (LGICs) play an important role in fast synaptic signal transduction. Binding of agonists to the β-sheet-structured extracellular domain opens an ion channel in the transmembrane α-helical region of the LGIC. How the structurally distinct and distant domains are functionally coupled for such central transmembrane signaling processes remains an open question. To obtain detailed information about the stability of and the coupling between these different functional domains, we analyzed the thermal unfolding of a homopentameric LGIC, the 5-hydroxytryptamine receptor (ligand binding, secondary structure, accessibility of Trp and Cys residues, and aggregation), in plasma membranes as well as during detergent extraction, purification, and reconstitution into artificial lipid bilayers. We found a large loss in thermostability correlating with the loss of the lipid bilayer during membrane solubilization and purification. Thermal unfolding of the 5-hydroxytryptamine receptor occurred in consecutive steps at distinct protein locations. A loss of ligand binding was detected first, followed by formation of different transient low oligomeric states of receptor pentamers, followed by partial unfolding of helical parts of the protein, which finally lead to the formation receptor aggregates. Structural destabilization of the receptor in detergents could be partially reversed by reconstituting the receptor into lipid bilayers. Our results are important because they quantify the stability of LGICs during detergent extraction and purification and can be used to create stabilized receptor proteins for structural and functional studies.
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Affiliation(s)
- Menno B Tol
- Laboratory of Physical Chemistry of Polymers and Membranes, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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46
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López CJ, Oga S, Hubbell WL. Mapping molecular flexibility of proteins with site-directed spin labeling: a case study of myoglobin. Biochemistry 2012; 51:6568-83. [PMID: 22809279 DOI: 10.1021/bi3005686] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Site-directed spin labeling (SDSL) has potential for mapping protein flexibility under physiological conditions. The purpose of the present study was to explore this potential using 38 singly spin-labeled mutants of myoglobin distributed throughout the sequence. Correlation of the EPR spectra with protein structure provides new evidence that the site-dependent variation in line shape, and hence motion of the spin label, is due largely to differences in mobility of the helical backbone in the ns time range. Fluctuations between conformational substates, typically in the μs-ms time range, are slow on the EPR time scale, and the spectra provide a snapshot of conformational equilibria frozen in time as revealed by multiple components in the spectra. A recent study showed that osmolyte perturbation can positively identify conformational exchange as the origin of multicomponent spectra (López et al. (2009), Protein Sci. 18, 1637). In the present study, this new strategy is employed in combination with line shape analysis and pulsed-EPR interspin distance measurements to investigate the conformation and flexibility of myoglobin in three folded and partially folded states. The regions identified to be in conformational exchange in the three forms agree remarkably well with those assigned by NMR, but the faster time scale of EPR allows characterization of localized states not detected in NMR. Collectively, the results suggest that SDSL-EPR and osmolyte perturbation provide a facile means for mapping the amplitude of fast backbone fluctuations and for detecting sequences in slow conformational exchange in folded and partially folded protein sequences.
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Affiliation(s)
- Carlos J López
- Department of Chemistry and Biochemistry, Jules Stein Eye Institute, University of California, Los Angeles, CA 90095-7008, USA
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47
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Risso VA, Acierno JP, Capaldi S, Monaco HL, Ermácora MR. X-ray evidence of a native state with increased compactness populated by tryptophan-less B. licheniformis β-lactamase. Protein Sci 2012; 21:964-76. [PMID: 22496053 DOI: 10.1002/pro.2076] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 03/25/2012] [Accepted: 03/29/2012] [Indexed: 11/12/2022]
Abstract
β-lactamases confer antibiotic resistance, one of the most serious world-wide health problems, and are an excellent theoretical and experimental model in the study of protein structure, dynamics and evolution. Bacillus licheniformis exo-small penicillinase (ESP) is a Class-A β-lactamase with three tryptophan residues located in the protein core. Here, we report the 1.7-Å resolution X-ray structure, catalytic parameters, and thermodynamic stability of ESP(ΔW), an engineered mutant of ESP in which phenylalanine replaces the wild-type tryptophan residues. The structure revealed no qualitative conformational changes compared with thirteen previously reported structures of B. licheniformis β-lactamases (RMSD = 0.4-1.2 Å). However, a closer scrutiny showed that the mutations result in an overall more compact structure, with most atoms shifted toward the geometric center of the molecule. Thus, ESP(ΔW) has a significantly smaller radius of gyration (R(g)) than the other B. licheniformis β-lactamases characterized so far. Indeed, ESP(ΔW) has the smallest R(g) among 126 Class-A β-lactamases in the Protein Data Bank (PDB). Other measures of compactness, like the number of atoms in fixed volumes and the number and average of noncovalent distances, confirmed the effect. ESP(ΔW) proves that the compactness of the native state can be enhanced by protein engineering and establishes a new lower limit to the compactness of the Class-A β-lactamase fold. As the condensation achieved by the native state is a paramount notion in protein folding, this result may contribute to a better understanding of how the sequence determines the conformational variability and thermodynamic stability of a given fold.
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Affiliation(s)
- Valeria A Risso
- Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 325, 1876 Bernal, Buenos Aires, Argentina
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48
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Plapp BV, Ramaswamy S. Atomic-resolution structures of horse liver alcohol dehydrogenase with NAD(+) and fluoroalcohols define strained Michaelis complexes. Biochemistry 2012; 51:4035-48. [PMID: 22531044 DOI: 10.1021/bi300378n] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structures of horse liver alcohol dehydrogenase complexed with NAD(+) and unreactive substrate analogues, 2,2,2-trifluoroethanol or 2,3,4,5,6-pentafluorobenzyl alcohol, were determined at 100 K at 1.12 or 1.14 Å resolution, providing estimates of atomic positions with overall errors of ~0.02 Å, the geometry of ligand binding, descriptions of alternative conformations of amino acid residues and waters, and evidence of a strained nicotinamide ring. The four independent subunits from the two homodimeric structures differ only slightly in the peptide backbone conformation. Alternative conformations for amino acid side chains were identified for 50 of the 748 residues in each complex, and Leu-57 and Leu-116 adopt different conformations to accommodate the different alcohols at the active site. Each fluoroalcohol occupies one position, and the fluorines of the alcohols are well-resolved. These structures closely resemble the expected Michaelis complexes with the pro-R hydrogens of the methylene carbons of the alcohols directed toward the re face of C4N of the nicotinamide rings with a C-C distance of 3.40 Å. The oxygens of the alcohols are ligated to the catalytic zinc at a distance expected for a zinc alkoxide (1.96 Å) and participate in a low-barrier hydrogen bond (2.52 Å) with the hydroxyl group of Ser-48 in a proton relay system. As determined by X-ray refinement with no restraints on bond distances and planarity, the nicotinamide rings in the two complexes are slightly puckered (quasi-boat conformation, with torsion angles of 5.9° for C4N and 4.8° for N1N relative to the plane of the other atoms) and have bond distances that are somewhat different compared to those found for NAD(P)(+). It appears that the nicotinamide ring is strained toward the transition state on the path to alcohol oxidation.
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Affiliation(s)
- Bryce V Plapp
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242, USA.
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49
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Sugiyama S, Maruyama M, Sazaki G, Hirose M, Adachi H, Takano K, Murakami S, Inoue T, Mori Y, Matsumura H. Growth of protein crystals in hydrogels prevents osmotic shock. J Am Chem Soc 2012; 134:5786-9. [PMID: 22435400 DOI: 10.1021/ja301584y] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
High-throughput protein X-ray crystallography offers a significant opportunity to facilitate drug discovery. The most reliable approach is to determine the three-dimensional structure of the protein-ligand complex by soaking the ligand in apo crystals. However, protein apo crystals produced by conventional crystallization in a solution are fatally damaged by osmotic shock during soaking. To overcome this difficulty, we present a novel technique for growing protein crystals in a high-concentration hydrogel that is completely gellified and exhibits high strength. This technique allowed us essentially to increase the mechanical stability of the crystals, preventing serious damage to the crystals caused by osmotic shock. Thus, this method may accelerate structure-based drug discoveries.
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Affiliation(s)
- Shigeru Sugiyama
- Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
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50
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Accessing protein conformational ensembles using room-temperature X-ray crystallography. Proc Natl Acad Sci U S A 2011; 108:16247-52. [PMID: 21918110 DOI: 10.1073/pnas.1111325108] [Citation(s) in RCA: 447] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Modern protein crystal structures are based nearly exclusively on X-ray data collected at cryogenic temperatures (generally 100 K). The cooling process is thought to introduce little bias in the functional interpretation of structural results, because cryogenic temperatures minimally perturb the overall protein backbone fold. In contrast, here we show that flash cooling biases previously hidden structural ensembles in protein crystals. By analyzing available data for 30 different proteins using new computational tools for electron-density sampling, model refinement, and molecular packing analysis, we found that crystal cryocooling remodels the conformational distributions of more than 35% of side chains and eliminates packing defects necessary for functional motions. In the signaling switch protein, H-Ras, an allosteric network consistent with fluctuations detected in solution by NMR was uncovered in the room-temperature, but not the cryogenic, electron-density maps. These results expose a bias in structural databases toward smaller, overpacked, and unrealistically unique models. Monitoring room-temperature conformational ensembles by X-ray crystallography can reveal motions crucial for catalysis, ligand binding, and allosteric regulation.
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