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Xu J, Wang S, Zhao WJ, Xi YB, Yan YB, Yao K. The congenital cataract-linked A2V mutation impairs tetramer formation and promotes aggregation of βB2-crystallin. PLoS One 2012; 7:e51200. [PMID: 23236454 PMCID: PMC3516508 DOI: 10.1371/journal.pone.0051200] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 10/30/2012] [Indexed: 11/28/2022] Open
Abstract
β/γ-Crystallins, the major structural proteins in human lens, are highly conserved in their tertiary structures but distinct in the quaternary structures. The N- and C-terminal extensions have been proposed to play a crucial role in mediating the size of β-crystallin assembly. In this research, we investigated the molecular mechanism underlying the congenital hereditary cataract caused by the recently characterized A2V mutation in βB2-crystallin. Spectroscopic experiments indicated that the mutation did not affect the secondary and tertiary structures of βB2-crystallin. The mutation did not affect the formation of βB2/βA3-crystallin heteromer as well as the stability and folding of the heteromer, suggesting that the mutation might not interfere with the protein interacting network in the lens. However, the tetramerization of βB2-crystallin at high protein concentrations was retarded by the A2V mutation. The mutation slightly decreased the thermal stability and promoted the thermal aggregation of βB2-crystallin. Although it did not influence the stability of βB2-crystallin against denaturation induced by chemical denaturants and UV irradiation, the A2V mutant was more prone to be trapped in the off-pathway aggregation process during kinetic refolding. Our results suggested that the A2V mutation might lead to injury of lens optical properties by decreasing βB2-crystallin stability against heat treatment and by impairing βB2-crystallin assembly into high-order homo-oligomers.
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Affiliation(s)
- Jia Xu
- Eye Center of the 2nd Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China
| | - Sha Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Wei-Jie Zhao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yi-Bo Xi
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
- Institute of Biophysics, Lanzhou University, Lanzhou, China
| | - Yong-Bin Yan
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
- * E-mail: (Y-BY); (KY)
| | - Ke Yao
- Eye Center of the 2nd Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China
- * E-mail: (Y-BY); (KY)
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Wang S, Leng XY, Yan YB. The Benefits of Being β-Crystallin Heteromers: βB1-Crystallin Protects βA3-Crystallin against Aggregation during Co-refolding. Biochemistry 2011; 50:10451-61. [DOI: 10.1021/bi201375p] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Sha Wang
- State Key
Laboratory of Biomembrane and Membrane Biotechnology, School of Life
Sciences, Tsinghua University, Beijing
100084, China
| | - Xiao-Yao Leng
- State Key
Laboratory of Biomembrane and Membrane Biotechnology, School of Life
Sciences, Tsinghua University, Beijing
100084, China
| | - Yong-Bin Yan
- State Key
Laboratory of Biomembrane and Membrane Biotechnology, School of Life
Sciences, Tsinghua University, Beijing
100084, China
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3
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McHaourab HS, Godar JA, Stewart PL. Structure and mechanism of protein stability sensors: chaperone activity of small heat shock proteins. Biochemistry 2009; 48:3828-37. [PMID: 19323523 DOI: 10.1021/bi900212j] [Citation(s) in RCA: 205] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Small heat shock proteins (sHSP) make up a remarkably diverse group of molecular chaperones possessing a degree of structural plasticity unparalleled in other protein superfamilies. In the absence of chemical energy input, these stability sensors can sensitively recognize and bind destabilized proteins, even in the absence of gross misfolding. Cellular conditions regulate affinity toward client proteins, allowing tightly controlled switching and tuning of sHSP chaperone capacity. Perturbations of this regulation, through chemical modification or mutation, directly lead to a variety of disease states. This review explores the structural basis of sHSP oligomeric flexibility and the corresponding functional consequences in the context of a model describing sHSP activity with a set of three coupled thermodynamic equilibria. As current research illuminates many novel physiological roles for sHSP outside of their traditional duties as molecular chaperones, such a conceptual framework provides a sound foundation for describing these emerging functions in physiological and pathological processes.
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Affiliation(s)
- Hassane S McHaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232-0615, USA.
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Gráczer É, Varga A, Melnik B, Semisotnov G, Závodszky P, Vas M. Symmetrical Refolding of Protein Domains and Subunits: Example of the Dimeric Two-Domain 3-Isopropylmalate Dehydrogenases. Biochemistry 2009; 48:1123-34. [DOI: 10.1021/bi801857t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Éva Gráczer
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary, and Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Andrea Varga
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary, and Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Bogdan Melnik
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary, and Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Gennady Semisotnov
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary, and Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Péter Závodszky
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary, and Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Mária Vas
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary, and Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
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5
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Disulfide cross-links in the interaction of a cataract-linked alphaA-crystallin mutant with betaB1-crystallin. FEBS Lett 2008; 583:175-9. [PMID: 19071118 DOI: 10.1016/j.febslet.2008.11.047] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Revised: 10/18/2008] [Accepted: 11/06/2008] [Indexed: 11/23/2022]
Abstract
A number of alphaA-crystallin mutants are associated with hereditary cataract including cysteine substitution at arginine 49. We report the formation of affinity-driven disulfide bonds in the interaction of alphaA-R49C with betaB1-crystallin. To mimic cysteine thiolation in the lens, betaB1-crystallin was modified by a bimane probe through a disulfide linkage. Our data suggest a mechanism whereby a transient disulfide bond occurs between alphaA- and betaB1-crystallin followed by a disulfide exchange with cysteine 49 of a neighboring alphaA-crystallin subunit. This is the first investigation of disulfide bonds in the confine of the chaperone/substrate complex where reaction rates are favored by orders of magnitude. Covalent protein cross-links are a hallmark of age-related cataract and may be a factor in its inherited form.
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6
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Takata T, Oxford JT, Demeler B, Lampi KJ. Deamidation destabilizes and triggers aggregation of a lens protein, betaA3-crystallin. Protein Sci 2008; 17:1565-75. [PMID: 18567786 DOI: 10.1110/ps.035410.108] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Protein aggregation is a hallmark of several neurodegenerative diseases and also of cataracts. The major proteins in the lens of the eye are crystallins, which accumulate throughout life and are extensively modified. Deamidation is the major modification in the lens during aging and cataracts. Among the crystallins, the betaA3-subunit has been found to have multiple sites of deamidation associated with the insoluble proteins in vivo. Several sites were predicted to be exposed on the surface of betaA3 and were investigated in this study. Deamidation was mimicked by site-directed mutagenesis at Q42 and N54 on the N-terminal domain, N133 and N155 on the C-terminal domain, and N120 in the peptide connecting the domains. Deamidation altered the tertiary structure without disrupting the secondary structure or the dimer formation of betaA3. Deamidations in the C-terminal domain and in the connecting peptide decreased stability to a greater extent than deamidations in the N-terminal domain. Deamidation at N54 and N155 also disrupted the association with the betaB1-subunit. Sedimentation velocity experiments integrated with high-resolution analysis detected soluble aggregates at 15%-20% in all deamidated proteins, but not in wild-type betaA3. These aggregates had elevated frictional ratios, suggesting that they were elongated. The detection of aggregates in vitro strongly suggests that deamidation may contribute to protein aggregation in the lens. A potential mechanism may include decreased stability and/or altered interactions with other beta-subunits. Understanding the role of deamidation in the long-lived crystallins has important implications in other aggregation diseases.
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Affiliation(s)
- Takumi Takata
- Department of Integrative Biosciences, School of Dentistry, Oregon Health and Science University, Portland, Oregon 97239-3098, USA
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Rumfeldt JAO, Galvagnion C, Vassall KA, Meiering EM. Conformational stability and folding mechanisms of dimeric proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:61-84. [PMID: 18602415 DOI: 10.1016/j.pbiomolbio.2008.05.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The folding of multisubunit proteins is of tremendous biological significance since the large majority of proteins exist as protein-protein complexes. Extensive experimental and computational studies have provided fundamental insights into the principles of folding of small monomeric proteins. Recently, important advances have been made in extending folding studies to multisubunit proteins, in particular homodimeric proteins. This review summarizes the equilibrium and kinetic theory and models underlying the quantitative analysis of dimeric protein folding using chemical denaturation, as well as the experimental results that have been obtained. Although various principles identified for monomer folding also apply to the folding of dimeric proteins, the effects of subunit association can manifest in complex ways, and are frequently overlooked. Changes in molecularity typically give rise to very different overall folding behaviour than is observed for monomeric proteins. The results obtained for dimers have provided key insights pertinent to understanding biological assembly and regulation of multisubunit proteins. These advances have set the stage for future advances in folding involving protein-protein interactions for natural multisubunit proteins and unnatural assemblies involved in disease.
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Affiliation(s)
- Jessica A O Rumfeldt
- Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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Claxton DP, Zou P, Mchaourab HS. Structure and orientation of T4 lysozyme bound to the small heat shock protein alpha-crystallin. J Mol Biol 2007; 375:1026-39. [PMID: 18062989 DOI: 10.1016/j.jmb.2007.11.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 10/17/2007] [Accepted: 11/06/2007] [Indexed: 10/22/2022]
Abstract
We have determined the structural changes that accompany the formation of a stable complex between a destabilized mutant of T4 lysozyme (T4L) and the small heat shock protein alpha-crystallin. Using pairs of fluorescence or spin label probes to fingerprint the T4L tertiary fold, we demonstrate that binding disrupts tertiary packing in the two domains as well as across the active-site cleft. Furthermore, increased distances between i and i+4 residues of helices support a model in which the bound structure is not native-like but significantly unfolded. In the confines of the oligomer, T4L has a preferential orientation with residues in the more hydrophobic C-terminal domain sequestered in a buried environment, while residues in the N-terminal domain are exposed to the aqueous solvent. Furthermore, electron paramagnetic resonance spectral line shapes of sites in the N-terminal domain are narrower than in the folded, unbound T4L reflecting an unstructured backbone and an asymmetric pattern of contacts between T4L and alpha-crystallin. The net orientation is not affected by the location of the destabilizing mutation consistent with the notion that binding is not triggered by recognition of localized unfolding. Together, the structural and thermodynamic data indicate that the stably bound conformation of T4L is unfolded and support a model in which the two modes of substrate binding originate from two discrete binding sites on the chaperone.
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Affiliation(s)
- Derek P Claxton
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, 741 Light Hall, 2215 Garland Avenue, Nashville, TN 37232, USA
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McHaourab HS, Kumar MS, Koteiche HA. Specificity of alphaA-crystallin binding to destabilized mutants of betaB1-crystallin. FEBS Lett 2007; 581:1939-43. [PMID: 17449033 PMCID: PMC2219212 DOI: 10.1016/j.febslet.2007.04.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 03/29/2007] [Accepted: 04/02/2007] [Indexed: 11/27/2022]
Abstract
To elucidate the structural and energetic basis of attractive protein interactions in the aging lens, we investigated the binding of destabilized mutants of betaB1-crystallin to the lens chaperones, alpha-crystallins. We show that the mutations enhance the binding affinity to alphaA- but not alphaB-crystallin at physiological temperatures. Complex formation disrupts the dimer interface of betaB1-crystallin consistent with the binding of a monomer. Binding isotherms obtained at increasing concentrations of betaB1-crystallin deviate from a classic binding equilibrium and display cooperative-like behavior. In the context of betaB1-crystallin unfolding equilibrium, these characteristics are reflective of the concentration-dependent change in the population of a dimeric intermediate that has low affinity to alphaA-crystallin. In the lens, where alpha-crystallin binding sites are not regenerated, this may represent an added mechanism to maintain lens transparency.
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Affiliation(s)
- Hassane S McHaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
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