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Ghosh D, Agarwal M, Radhakrishna M. Molecular Insights into the Inhibitory Role of α-Crystallin against γD-Crystallin Aggregation. J Chem Theory Comput 2024; 20:1740-1752. [PMID: 38078935 DOI: 10.1021/acs.jctc.3c00774] [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: 12/21/2023]
Abstract
Cataracts, a major cause of global blindness, contribute significantly to the overall prevalence of blindness. The opacification of the lens, resulting in cataract formation, primarily occurs due to the aggregation of crystallin proteins within the eye lens. Despite the high concentration of these crystallins, they remarkably maintain the lens transparency and refractive index. α-Crystallins (α-crys), acting as chaperones, play a crucial role in preventing crystallin aggregation, although the exact molecular mechanism remains uncertain. In this study, we employed a combination of molecular docking, all-atom molecular dynamics simulations, and advanced free energy calculations to investigate the interaction between γD-crystallin (γD-crys), a major structural protein of the eye lens, and α-crystallin proteins. Our findings demonstrate that α-crys exhibits an enhanced affinity for the NTD2 and CTD4 regions of γD-crys. The NTD2 and CTD4 regions form the interface between the N-terminal domain (NTD) and the C-terminal domain (CTD) of the γD-crys protein. By binding to the interface region between the NTD and CTD of the protein, α-crys effectively inhibits the formation of domain-swapped aggregates and mitigates protein aggregation. Analysis of the Markov state models using molecular dynamics trajectories confirms that minimum free energy conformations correspond to the binding of the α-crystallin domain (ACD) of α-crys to NTD2 and CTD4 that form the interdomain interface.
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Affiliation(s)
- Deepshikha Ghosh
- Department of Biological Sciences and Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat 382355, India
| | - Manish Agarwal
- Computer Services Centre, Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi, Delhi 110016, India
| | - Mithun Radhakrishna
- Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat 382355, India
- Center for Biomedical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat 382355, India
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2
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Ghosh D, Sojitra KA, Biswas A, Agarwal M, Radhakrishna M. Effect of mutations on the folding and stability of γD-crystallin protein. J Biomol Struct Dyn 2023:1-15. [PMID: 37830785 DOI: 10.1080/07391102.2023.2266768] [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: 05/08/2023] [Accepted: 09/25/2023] [Indexed: 10/14/2023]
Abstract
Interprotein interactions between the partially unfolded states of γD-crystallin (γD-crys) protein are known to cause cataracts. Therefore, understanding the unfolding pathways of native γD-crys is extremely crucial to delineate their aggregation mechanism. In this study, we have performed extensive all-atom Molecular Dynamics simulations with explicit solvent to understand the role of the critical residues that drive the stability of the motifs and domains of γD-crys in its wild type and mutant forms. Our findings show that while the individual motifs of wild type are not stable in the native form, the individual domains remain structurally stable at 425K. This enhanced stability of the domain was attributed to the hydrophobic interactions between the motifs. Single and double point mutations of the domains with negatively charged aspartic and glutamic acid amino acid residues (I3E, W42D, W42E, I3D/W42D, I3E/W42E, and L92D/W157D) decreases the structural stability, leading to unfolding of individual domains of γD-crys. We believe that our study sheds light on the weakest links of γD-crys, along with the role of interactions stabilizing the domains. Further, this study bolsters and provides a better understanding of the domain swapping mechanism of aggregation of γD-crys.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Deepshikha Ghosh
- Department of Biological Sciences and Engineering, Indian Institute of Technology (IIT), Gandhinagar, Palaj, Gujarat, India
| | - Kandarp Ashokbhai Sojitra
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
| | - Anushka Biswas
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
| | - Manish Agarwal
- Computer Services Centre, Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi, Delhi
| | - Mithun Radhakrishna
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
- Center for Biomedical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
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3
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Khanijou JK, Yee Z, Raida M, Lee JM, Tay EZE, Gruber J, Walczyk T. Efficiency of Protein Renewal Is Limited by Feed Intake and Not by Protein Lifetime in Aging Caenorhabditis elegans. J Proteome Res 2022; 21:2664-2686. [PMID: 36181456 DOI: 10.1021/acs.jproteome.2c00383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein turnover maintains the proteome's functional integrity. Here, protein turnover efficiency over time in wild-type Caenorhabditis elegans was assessed using inverse [15N]-pulse labeling up to 7 days after the egg-laying phase at 20 °C. Isotopic analysis of some abundant proteins was executed favoring data quality over quantity for mathematical modeling. Surprisingly, isotopic enrichment over time reached an upper limit showing an apparent cessation of protein renewal well before death, with protein fractions inaccessible to turnover ranging from 14 to 83%. For life span modulation, worms were raised at different temperatures after egg laying. Mathematical modeling of isotopic enrichment points either to a slowdown of protein turnover or to an increasing protein fraction resistant to turnover with time. Most notably, the estimated time points of protein turnover cessation from our mathematical model were highly correlated with the observed median life span. Thrashing and pumping rates over time were linearly correlated with isotopic enrichment, therefore linking protein/tracer intake to protein turnover rate and protein life span. If confirmed, life span extension is possible by optimizing protein turnover rate through modulating protein intake in C. elegans and possibly other organisms. While proteome maintenance benefits from a high protein turnover rate, protein turnover is fundamentally energy-intensive, where oxidative stress contributes to damage that it is supposed to repair.
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Affiliation(s)
- Jasmeet Kaur Khanijou
- Department of Chemistry, National University of Singapore (NUS), Singapore 117543, Singapore.,Shared Analytics, Singapore Institute of Food and Biotechnology Innovation (SIFBI), Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore
| | - Zhuangli Yee
- Yale-NUS College, Singapore 138527, Singapore.,Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 117597, Singapore
| | - Manfred Raida
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 117597, Singapore.,Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore
| | - Jin Meng Lee
- Department of Chemistry, National University of Singapore (NUS), Singapore 117543, Singapore
| | - Evan Zhi En Tay
- Department of Chemistry, National University of Singapore (NUS), Singapore 117543, Singapore
| | - Jan Gruber
- Yale-NUS College, Singapore 138527, Singapore.,Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 117597, Singapore
| | - Thomas Walczyk
- Department of Chemistry, National University of Singapore (NUS), Singapore 117543, Singapore
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Hsueh SS, Wang SS(S, Chen SH, Wang CL, Wu W(J, Lin TH. Insights to Human γD-Crystallin Unfolding by NMR Spectroscopy and Molecular Dynamics Simulations. Int J Mol Sci 2022; 23:ijms23031591. [PMID: 35163513 PMCID: PMC8836049 DOI: 10.3390/ijms23031591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 01/13/2022] [Accepted: 01/19/2022] [Indexed: 11/16/2022] Open
Abstract
Human γD-crystallin (HGDC) is an abundant lens protein residing in the nucleus of the human lens. Aggregation of this and other structural proteins within the lens leads to the development of cataract. Much has been explored on the stability and aggregation of HGDC and where detailed investigation at the atomic resolution was needed, the X-ray structure was used as an initial starting conformer for molecular modeling. In this study, we implemented NMR-solution HGDC structures as starting conformers for molecular dynamics simulations to provide the missing pieces of the puzzle on the very early stages of HGDC unfolding leading up to the domain swap theories proposed by past studies. The high-resolution details of the conformational dynamics also revealed additional insights to possible early intervention for cataractogenesis.
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Affiliation(s)
- Shu-Shun Hsueh
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; (S.-S.H.); (S.-S.W.); (S.-H.C.)
| | - S.-S. (Steven) Wang
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; (S.-S.H.); (S.-S.W.); (S.-H.C.)
| | - Shu-Han Chen
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; (S.-S.H.); (S.-S.W.); (S.-H.C.)
| | - Chia-Lin Wang
- Laboratory of Nuclear Magnetic Resonance, Medical Research Department, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
| | - W. (Josephine) Wu
- Department of Optometry, Yuanpei University of Medical Technology, Hsinchu City 30015, Taiwan
- Correspondence: (J.W.W.); (T.-H.L.); Tel.: +886-3-538-1183 (ext. 8608) (W.W.); +886-2-28712121 (ext. 2703) (T.-H.L.)
| | - Ta-Hsien Lin
- Laboratory of Nuclear Magnetic Resonance, Medical Research Department, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei 11221, Taiwan
- Correspondence: (J.W.W.); (T.-H.L.); Tel.: +886-3-538-1183 (ext. 8608) (W.W.); +886-2-28712121 (ext. 2703) (T.-H.L.)
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Abstract
The crystallins (α, β and γ), major constituent proteins of eye lens fiber cells play their critical role in maintaining the transparency and refractive index of the lens. Under different stress factors and with aging, β- and γ-crystallins start to unfold partially leading to their aggregation. Protein aggregation in lens basically enhances light scattering and causes the vision problem, commonly known as cataract. α-crystallin as a molecular chaperone forms complexes with its substrates (β- and γ-crystallins) to prevent such aggregation. In this chapter, the structural features of β- and γ-crystallins have been discussed. Detailed structural information linked with the high stability of γC-, γD- and γS-crystallins have been incorporated. The nature of homologous and heterologous interactions among crystallins has been deciphered, which are involved in their molecular association and complex formation.
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Affiliation(s)
- Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, 177005, Himachal Pradesh, India.
| | - Priyanka Chauhan
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, 177005, Himachal Pradesh, India
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Cui H, Gu Z, Chen X, Lin L, Wang Z, Dai X, Yang Z, Liu L, Zhou R, Dong M. Stimulating antibacterial activities of graphitic carbon nitride nanosheets with plasma treatment. NANOSCALE 2019; 11:18416-18425. [PMID: 31576862 DOI: 10.1039/c9nr03797g] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
As a widely studied photoactive antibacterial nanomaterial, the intrinsic antibacterial traits of graphitic carbon nitride (g-C3N4) as a two-dimensional nanomaterial have not been reported so far. Herein, nitrogen-plasma-treated g-C3N4 (N-g-C3N4) nanosheets and their influence on bactericidal characteristics are investigated. Bactericidal rates of more than 99% have been successfully achieved for 8 kinds of foodborne pathogenic bacteria by N-g-C3N4 with 8 h incubation in the dark. The achieved rates are percentage wise 10 times higher than those for pristine g-C3N4. Cell rupture caused by direct mechanical contact between g-C3N4 nanosheets and cell membranes is observed. X-ray photoelectron spectroscopy revealed a substantial loss of surface defects and nitrogen vacancies in N-g-C3N4. Molecular dynamics simulations further indicated that the largely sealed defects of N-g-C3N4 enhanced the electrostatic attraction between inherent pores and lipid heads; thus, further insertion of N-g-C3N4 was promoted, resulting in enhanced antibacterial activity. This study establishes novel fabrication and application strategies for carbon based antibacterial nanomaterials.
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Affiliation(s)
- Haiying Cui
- School of Food & Biological Engineering, Jiangsu University, Zhenjiang 212013, China.
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7
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Zhou H, Liu S, Yin X, Li Z, Yang Z, Zhou R. Molecular Origin of the Stability Difference in Four Shark IgNAR Constant Domains. Biophys J 2019; 116:1907-1917. [PMID: 31060814 DOI: 10.1016/j.bpj.2019.04.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 02/09/2019] [Accepted: 04/15/2019] [Indexed: 12/11/2022] Open
Abstract
Improving the stability of antibodies for manufacture and shelf life is one of the main focuses of antibody engineering. One stabilization strategy is to perform specific mutations in human antibodies based on highly stable antibodies in other species. To identify the key residues for mutagenesis, it is necessary to understand the roles of these residues in stabilizing the antibody. Here, we use molecular dynamics simulations to study the molecular origin of the four shark immunoglobulin new antigen receptors constant domains (C1-C4). According to the unfolding pathways and the conformational free energy surfaces in 8 M urea at 380 K, the C2 domain is the most stable, followed by C4, C1, and C3, which agrees with the experimental findings. The C1 and C3 domains follow a common unfolding pathway in which the unfolding starts from the edge strands, particularly strand g, and then gradually progresses to the inner strands. Detailed structural analysis of the C2 domain reveals a "sandwich-like" R339-E322-R341 salt-bridge cluster on strand g, which grants ultrahigh stability to the C2 domain. We further design two sets of mutations by mutating E322 to alanine or setting all atomic charges in E322 to zero to break the salt-bridge cluster in the C2 domain, which confirms the importance of the salt bridges in stability. In the C4 domain, the D80-K104 salt bridge on strand g also strengthens the stability. On the other hand, in the C1 and C3 domains, there is no salt bridge on strand g. In addition to the salt bridges, the overall hydrophobicity score of the hydrophobic core is also positively correlated with the domain stability. Our findings provide a detailed microscopic picture of the molecular origin of the four shark immunoglobulin new antigen receptors constant domains that not only explains the differences in their structural stability but also provides important insights into future antibody design.
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Affiliation(s)
- Hong Zhou
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China
| | - Shengtang Liu
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China
| | - Xiuhua Yin
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China
| | - Zengpeng Li
- State Key Laboratory Breeding Base of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources, Fujian Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen, Fujian, China
| | - Zaixing Yang
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China.
| | - Ruhong Zhou
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China; IBM Thomas J. Watson Research Center, Yorktown Heights, New York; Department of Chemistry, Columbia University, New York, New York.
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8
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Kang H, Yang Z, Zhou R. Lanosterol Disrupts Aggregation of Human γD-Crystallin by Binding to the Hydrophobic Dimerization Interface. J Am Chem Soc 2018; 140:8479-8486. [DOI: 10.1021/jacs.8b03065] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Hongsuk Kang
- Institute of Quantitative Biology, Department of Physics, Zhejiang University, Hangzhou 310027, China
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
| | - Zaixing Yang
- State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X) and Collaborative Innovation Centre of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China
| | - Ruhong Zhou
- Institute of Quantitative Biology, Department of Physics, Zhejiang University, Hangzhou 310027, China
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
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Vendra VPR, Khan I, Chandani S, Muniyandi A, Balasubramanian D. Gamma crystallins of the human eye lens. Biochim Biophys Acta Gen Subj 2015; 1860:333-43. [PMID: 26116913 DOI: 10.1016/j.bbagen.2015.06.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 06/08/2015] [Accepted: 06/19/2015] [Indexed: 01/12/2023]
Abstract
BACKGROUND Protein crystallins co me in three types (α, β and γ) and are found predominantly in the eye, and particularly in the lens, where they are packed into a compact, plastic, elastic, and transparent globule of proper refractive power range that aids in focusing incoming light on to the retina. Of these, the γ-crystallins are found largely in the nuclear region of the lens at very high concentrations (>400 mg/ml). The connection between their structure and inter-molecular interactions and lens transparency is an issue of particular interest. SCOPE OF REVIEW We review the origin and phylogeny of the gamma crystallins, their special structure involving the use of Greek key supersecondary structural motif, and how they aid in offering the appropriate refractive index gradient, intermolecular short range attractive interactions (aiding in packing them into a transparent ball), the role that several of the constituent amino acid residues play in this process, the thermodynamic and kinetic stability and how even single point mutations can upset this delicate balance and lead to intermolecular aggregation, forming light-scattering particles which compromise transparency. We cite several examples of this, and illustrate this by cloning, expressing, isolating and comparing the properties of the mutant protein S39C of human γS-crystallin (associated with congenital cataract-microcornea), with those of the wild type molecule. In addition, we note that human γ-crystallins are also present in other parts of the eye (e.g., retina), where their functions are yet to be understood. MAJOR CONCLUSIONS There are several 'crucial' residues in and around the Greek key motifs which are essential to maintain the compact architecture of the crystallin molecules. We find that a mutation that replaces even one of these residues can lead to reduction in solubility, formation of light-scattering particles and loss of transparency in the molecular assembly. GENERAL SIGNIFICANCE Such a molecular understanding of the process helps us construct the continuum of genotype-molecular structural phenotype-clinical (pathological) phenotype. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Venkata Pulla Rao Vendra
- Ophthalmic Molecular Genetics Section, National Eye Institute, Building 5635FL, Room 1S24, 5625 Fishers Lane, Rockville, MD 20852, United States.
| | - Ismail Khan
- Prof. Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, L. V. Prasad Eye Institute, Hyderabad 500034 Telangana, India.
| | - Sushil Chandani
- Plot 32, LIC Colony, W Marredpally, Secunderabad 500026, Telangana, India.
| | - Anbukkarasi Muniyandi
- Department of Animal Science, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
| | - Dorairajan Balasubramanian
- Prof. Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, L. V. Prasad Eye Institute, Hyderabad 500034 Telangana, India.
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Serebryany E, King JA. The βγ-crystallins: native state stability and pathways to aggregation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:32-41. [PMID: 24835736 DOI: 10.1016/j.pbiomolbio.2014.05.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 04/30/2014] [Accepted: 05/02/2014] [Indexed: 01/26/2023]
Abstract
The βγ-crystallins are among the most stable and long-lived proteins in the human body. With increasing age, however, they transform to high molecular weight light-scattering aggregates, resulting in cataracts. This occurs despite the presence in the lens of high concentrations of the a-crystallin chaperones. Aggregation of crystallins can be induced in vitro by a variety of stresses, including acidic pH, ultraviolet light, oxidative damage, heating or freezing, and specific amino acid substitutions. Accumulating evidence points to the existence of specific biochemical pathways of protein: protein interaction and polymerization. We review the methods used for studying crystallin stability and aggregation and discuss the sometimes counterintuitive relationships between factors that favor native state stability and those that favor non-native aggregation. We discuss the behavior of βγ-crystallins in mixtures and their chaperone ability; the consequences of missense mutations and covalent damage to the side-chains; and the evolutionary strategies that have shaped these proteins. Efforts are ongoing to reveal the nature of cataractous crystallin aggregates and understand the mechanisms of aggregation in the context of key models of protein polymerization: amyloid, native-state, and domain-swapped. Such mechanistic understanding is likely to be of value for the development of therapeutic interventions and draw attention to unanswered questions about the relationship between a protein's native state stability and its transformation to an aggregated state.
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Affiliation(s)
- Eugene Serebryany
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Jonathan A King
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States.
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Schafheimer N, Wang Z, Schey K, King J. Tyrosine/cysteine cluster sensitizing human γD-crystallin to ultraviolet radiation-induced photoaggregation in vitro. Biochemistry 2014; 53:979-90. [PMID: 24410332 PMCID: PMC3954642 DOI: 10.1021/bi401397g] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
![]()
Ultraviolet
radiation (UVR) exposure is a major risk factor for
age-related cataract, a protein-aggregation disease of the human lens
often involving the major proteins of the lens, the crystallins. γD-Crystallin
(HγD-Crys) is abundant in the nucleus of the human lens, and
its folding and aggregation have been extensively studied. Previous
work showed that HγD-Crys photoaggregates in vitro upon exposure
to UVA/UVB light and that its conserved tryptophans are not required
for aggregation. Surprisingly, the tryptophan residues play a photoprotective
role because of a distinctive energy-transfer mechanism. HγD-Crys
also contains 14 tyrosine residues, 12 of which are organized as six
pairs. We investigated the role of the tyrosines of HγD-Crys
by replacing pairs with alanines and monitoring photoaggregation using
light scattering and SDS-PAGE. Mutating both tyrosines in the Y16/Y28
pair to alanine slowed the formation of light-scattering aggregates.
Further mutant studies implicated Y16 as important for photoaggregation.
Mass spectrometry revealed that C18, in contact with Y16, is heavily
oxidized during UVR exposure. Analysis of multiple mutant proteins
by mass spectrometry suggested that Y16 and C18 likely participate
in the same photochemical process. The data suggest an initial photoaggregation
pathway for HγD-Crys in which excited-state Y16 interacts with
C18, initiating radical polymerization.
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Affiliation(s)
- Nathaniel Schafheimer
- Department of Biology, Massachusetts Institute of Technology , 68-330, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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