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Kacirani A, Uralcan B, Domingues TS, Haji-Akbari A. Effect of Pressure on the Conformational Landscape of Human γD-Crystallin from Replica Exchange Molecular Dynamics Simulations. J Phys Chem B 2024; 128:4931-4942. [PMID: 38685567 DOI: 10.1021/acs.jpcb.4c00178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Human γD-crystallin belongs to a crucial family of proteins known as crystallins located in the fiber cells of the human lens. Since crystallins do not undergo any turnover after birth, they need to possess remarkable thermodynamic stability. However, their sporadic misfolding and aggregation, triggered by environmental perturbations or genetic mutations, constitute the molecular basis of cataracts, which is the primary cause of blindness in the globe according to the World Health Organization. Here, we investigate the impact of high pressure on the conformational landscape of wild-type HγD-crystallin using replica exchange molecular dynamics simulations augmented with principal component analysis. We find pressure to have a modest impact on global measures of protein stability, such as root-mean-square displacement and radius of gyration. Upon projecting our trajectories along the first two principal components from principal component analysis, however, we observe the emergence of distinct free energy basins at high pressures. By screening local order parameters previously shown or hypothesized as markers of HγD-crystallin stability, we establish correlations between a tyrosine-tyrosine aromatic contact within the N-terminal domain and the protein's end-to-end distance with projections along the first and second principal components, respectively. Furthermore, we observe the simultaneous contraction of the hydrophobic core and its intrusion by water molecules. This exploration sheds light on the intricate responses of HγD-crystallin to elevated pressures, offering insights into potential mechanisms underlying its stability and susceptibility to environmental perturbations, crucial for understanding cataract formation.
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Affiliation(s)
- Arlind Kacirani
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, United States
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, Connecticut 06520, United States
| | - Betül Uralcan
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, United States
- Department of Chemical Engineering, Boğaziçi University, Istanbul 34342, Turkey
| | - Tiago S Domingues
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, United States
- Graduate Program in Applied Mathematics, Yale University, New Haven, Connecticut 06520, United States
| | - Amir Haji-Akbari
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, United States
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Hill JA, Nyathi Y, Horrell S, von Stetten D, Axford D, Owen RL, Beddard GS, Pearson AR, Ginn HM, Yorke BA. An ultraviolet-driven rescue pathway for oxidative stress to eye lens protein human gamma-D crystallin. Commun Chem 2024; 7:81. [PMID: 38600176 PMCID: PMC11006947 DOI: 10.1038/s42004-024-01163-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/27/2024] [Indexed: 04/12/2024] Open
Abstract
Human gamma-D crystallin (HGD) is a major constituent of the eye lens. Aggregation of HGD contributes to cataract formation, the leading cause of blindness worldwide. It is unique in its longevity, maintaining its folded and soluble state for 50-60 years. One outstanding question is the structural basis of this longevity despite oxidative aging and environmental stressors including ultraviolet radiation (UV). Here we present crystallographic structures evidencing a UV-induced crystallin redox switch mechanism. The room-temperature serial synchrotron crystallographic (SSX) structure of freshly prepared crystallin mutant (R36S) shows no post-translational modifications. After aging for nine months in the absence of light, a thiol-adduct (dithiothreitol) modifying surface cysteines is observed by low-dose SSX. This is shown to be UV-labile in an acutely light-exposed structure. This suggests a mechanism by which a major source of crystallin damage, UV, may also act as a rescuing factor in a finely balanced redox system.
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Affiliation(s)
- Jake A Hill
- School of Chemistry and Biosciences, University of Bradford, Richmond Road, Bradford, BD7 1DP, United Kingdom
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
| | - Yvonne Nyathi
- Faculty of Biological Sciences, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
| | - Sam Horrell
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - David von Stetten
- European Molecular Biology Laboratory, Notkestraße 85, 22607, Hamburg, Germany
| | - Danny Axford
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - Robin L Owen
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - Godfrey S Beddard
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
- School of Chemistry, University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Arwen R Pearson
- HARBOR, Institute for Nanostructure and Solid State Physics, Hamburg, 22761, Germany
| | - Helen M Ginn
- HARBOR, Institute for Nanostructure and Solid State Physics, Hamburg, 22761, Germany.
- Center for Free-Electron Laser Science, CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607, Hamburg, Germany.
| | - Briony A Yorke
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom.
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Freites JA, Louis MN, Tobias DJ. Insights into the solubility of γ $$ \gamma $$ D-crystallin from multiscale atomistic simulations. J Comput Chem 2023. [PMID: 37093714 DOI: 10.1002/jcc.27116] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/31/2023] [Accepted: 04/12/2023] [Indexed: 04/25/2023]
Abstract
The molecular basis underlying the rich phase behavior of globular proteins remains poorly understood. We use atomistic multiscale molecular simulations to model the solution-state conformational dynamics and interprotein interactions of γ $$ \gamma $$ D-crystallin and its P23T-R36S mutant, which drastically limits the protein solubility, at both infinite dilution and at a concentration where the mutant fluid phase and crystalline phase coexist. We find that while the mutant conserves the protein fold, changes to the surface exposure of residues in the neighborhood of residue-36 enhance protein-protein interactions and develop specific protein-protein contacts found in the protein crystal lattice.
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Affiliation(s)
- J Alfredo Freites
- Department of Chemistry, University of California, Irvine, California, USA
| | - Mohab N Louis
- Department of Chemistry, University of California, Irvine, California, USA
| | - Douglas J Tobias
- Department of Chemistry, University of California, Irvine, California, USA
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Diessner EM, Freites JA, Tobias DJ, Butts CT. Network Hamiltonian Models for Unstructured Protein Aggregates, with Application to γD-Crystallin. J Phys Chem B 2023; 127:685-697. [PMID: 36637342 PMCID: PMC10437096 DOI: 10.1021/acs.jpcb.2c07672] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Network Hamiltonian models (NHMs) are a framework for topological coarse-graining of protein-protein interactions, in which each node corresponds to a protein, and edges are drawn between nodes representing proteins that are noncovalently bound. Here, this framework is applied to aggregates of γD-crystallin, a structural protein of the eye lens implicated in cataract disease. The NHMs in this study are generated from atomistic simulations of equilibrium distributions of wild-type and the cataract-causing variant W42R in solution, performed by Wong, E. K.; Prytkova, V.; Freites, J. A.; Butts, C. T.; Tobias, D. J. Molecular Mechanism of Aggregation of the Cataract-Related γD-Crystallin W42R Variant from Multiscale Atomistic Simulations. Biochemistry2019, 58 (35), 3691-3699. Network models are shown to successfully reproduce the aggregate size and structure observed in the atomistic simulation, and provide information about the transient protein-protein interactions therein. The system size is scaled from the original 375 monomers to a system of 10000 monomers, revealing a lowering of the upper tail of the aggregate size distribution of the W42R variant. Extrapolation to higher and lower concentrations is also performed. These results provide an example of the utility of NHMs for coarse-grained simulation of protein systems, as well as their ability to scale to large system sizes and high concentrations, reducing computational costs while retaining topological information about the system.
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Affiliation(s)
- Elizabeth M Diessner
- Department of Chemistry, University of California, Irvine, California92697, United States
| | - J Alfredo Freites
- Department of Chemistry, University of California, Irvine, California92697, United States
| | - Douglas J Tobias
- Department of Chemistry, University of California, Irvine, California92697, United States
| | - Carter T Butts
- Departments of Sociology, Statistics, Computer Science, and EECS, University of California, Irvine, California92697, United States
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Strofaldi A, Quinn MK, Seddon AM, McManus JJ. Polymorphic protein phase transitions driven by surface anisotropy. J Chem Phys 2023; 158:014905. [PMID: 36610968 DOI: 10.1063/5.0125452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Phase transitions of proteins are strongly influenced by surface chemical modifications or mutations. Human γD-crystallin (HGD) single-mutants have been extensively studied because they are associated with the onset of juvenile cataract. However, they have also provided a rich library of molecules to examine how specific inter-protein interactions direct protein assembly, providing new insights and valuable experimental data for coarse-grained patchy-particle models. Here, we demonstrate that the addition of new inter-protein interactions by mutagenesis is additive and increases the number and variety of condensed phases formed by proteins. When double mutations incorporating two specific single point mutations are made, the properties of both single mutations are retained in addition to the formation of a new condensed phase. We find that the HGD double-mutant P23VC110M self-assembles into spherical particles with retrograde solubility, orthorhombic crystals, and needle/plate shape crystals, while retaining the ability to undergo liquid-liquid phase separation. This rich polymorphism is only partially predicted by the experimental data on the constituent single mutants. We also report a previously un-characterized amorphous protein particle, with unique properties that differ from those of protein spherulites, protein particulates previously described. The particles we observe are amorphous, reversible with temperature, tens of microns in size, and perfectly spherical. When they are grown on pristine surfaces, they appear to form by homogeneous nucleation, making them unique, and we believe a new form of protein condensate. This work highlights the challenges in predicting protein behavior, which has frustrated rational assembly and crystallization but also provides rich data to develop new coarse-grained models to explain the observed polymorphism.
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Affiliation(s)
| | - Michelle K Quinn
- Department of Chemistry Maynooth University, Maynooth, Co. Kildare, Ireland
| | - Annela M Seddon
- HH Wills Physics Laboratory, School of Physics, University of Bristol, Bristol BS8 1TL, United Kingdom
| | - Jennifer J McManus
- HH Wills Physics Laboratory, School of Physics, University of Bristol, Bristol BS8 1TL, United Kingdom
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Strofaldi A, Khan AR, McManus JJ. Surface Exposed Free Cysteine Suppresses Crystallization of Human γD-Crystallin. J Mol Biol 2021; 433:167252. [PMID: 34537240 DOI: 10.1016/j.jmb.2021.167252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/06/2021] [Accepted: 09/09/2021] [Indexed: 11/28/2022]
Abstract
Human γD-crystallin (HGD) has remarkable stability against condensation in the human lens, sometimes over a whole lifetime. The native protein has a surface exposed free cysteine that forms dimers (Benedek, 1997; Ramkumar et al., 1864)1,2 without specific biological function and leads to further protein association and/or aggregation, which creates a paradox for understanding its stability. Previous work has demonstrated that chemical modification of the protein at the free cysteine (C110), increases the temperature at which liquid-liquid phase separation occurs (LLPS), lowers protein solubility and suggests an important role for this amino acid in maintaining its long-term resistance to condensation. Here we demonstrate that mutation of the cysteine does not alter the structure or solubility (liquidus) line for the protein, but dramatically increases the protein crystal nucleation rate following LLPS, suggesting that the free cysteine has a vital role in suppressing crystallization in the human lens.
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Affiliation(s)
- Alessandro Strofaldi
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland; H. H Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
| | - Amir R Khan
- Division of Newborn Medicine, Boston Children's Hospital, Boston, USA; School of Biochemistry, Trinity College Dublin, Ireland
| | - Jennifer J McManus
- H. H Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom.
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Altan I, Khan AR, James S, Quinn MK, McManus JJ, Charbonneau P. Using Schematic Models to Understand the Microscopic Basis for Inverted Solubility in γD-Crystallin. J Phys Chem B 2019; 123:10061-10072. [PMID: 31557434 DOI: 10.1021/acs.jpcb.9b07774] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Inverted solubility-melting a crystal by cooling-is observed in a handful of proteins, such as carbomonoxy hemoglobin C and γD-crystallin. In human γD-crystallin, the phenomenon is associated with the mutation of the 23rd residue, a proline, to a threonine, serine, or valine. One proposed microscopic mechanism entails an increase in surface hydrophobicity upon mutagenesis. Recent crystal structures of a double mutant that includes the P23T mutation allow for a more careful investigation of this proposal. Here, we first measure the surface hydrophobicity of various mutant structures of γD-crystallin and discern no notable increase in hydrophobicity upon mutating the 23rd residue. We then investigate the solubility inversion regime with a schematic patchy particle model that includes one of three variants of temperature-dependent patch energies: two of the hydrophobic effect, and one of a more generic nature. We conclude that, while solubility inversion due to the hydrophobic effect may be possible, microscopic evidence to support it in γD-crystallin is weak. More generally, we find that solubility inversion requires a fine balance between patch strengths and their temperature-dependent component, which may explain why inverted solubility is not commonly observed in proteins. We also find that the temperature-dependent interaction has only a negligible impact on liquid-liquid phase boundaries of γD-crystallin, in line with previous experimental observations.
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Affiliation(s)
| | - Amir R Khan
- School of Biochemistry and Immunology , Trinity College Dublin , Dublin , Ireland
| | - Susan James
- Department of Chemistry , Maynooth University , Maynooth , Ireland
| | - Michelle K Quinn
- Department of Chemistry , Maynooth University , Maynooth , Ireland
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