1
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Patel S, Hosur RV. Replica exchange molecular dynamics simulations reveal self-association sites in M-crystallin caused by mutations provide insights of cataract. Sci Rep 2021; 11:23270. [PMID: 34857812 PMCID: PMC8639718 DOI: 10.1038/s41598-021-02728-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 11/09/2021] [Indexed: 11/09/2022] Open
Abstract
Crystallins are ubiquitous, however, prevalence is seen in eye lens. Eye lens crystallins are long-lived and structural intactness is required for maintaining lens transparency and protein solubility. Mutations in crystallins often lead to cataract. In this study, we performed mutations at specific sites of M-crystallin, a close homologue of eye lens crystallin and studied by using replica exchange molecular dynamics simulation with generalized Born implicit solvent model. Mutations were made on the Ca2+ binding residues (K34D and S77D) and in the hydrophobic core (W45R) which is known to cause congenital cataract in homologous γD-crystallin. The chosen mutations caused large motion of the N-terminal Greek key, concomitantly broke the interlocking Greek keys interactions and perturbed the compact core resulting in several folded and partially unfolded states. Partially unfolded states exposed large hydrophobic patches that could act as precursors for self-aggregation. Accumulation of such aggregates is the potential cause of cataract in homologous eye lens crystallins.
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Affiliation(s)
- Sunita Patel
- UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Vidyanagari, Mumbai, 400098, India.
| | - Ramakrishna V. Hosur
- grid.452882.1UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Vidyanagari, Mumbai, 400098 India
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2
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Velasco-Bolom JL, Domínguez L. Exploring the folding process of human βB2-crystallin using multiscale molecular dynamics and the Markov state model. Phys Chem Chem Phys 2021; 22:26753-26763. [PMID: 33205789 DOI: 10.1039/d0cp04136j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Adequate knowledge of protein conformations is crucial for understanding their function and their association properties with other proteins. The cataract disease is correlated with conformational changes in key proteins called crystallins. These changes are due to mutations or post-translational modifications that may lead to protein unfolding, and thus the formation of aggregate states. Human βB2-crystallin (HβB2C) is found in high proportion in the eye lens, and its mutations are related to some cataracts. HβB2C also associates into dimers, tetramers, and other higher-order supramolecular complexes. However, it is the only protein of the βγ-crystallin family that has been found in an extended conformation. Therefore, we hypothesize that the extended conformation is not energetically favourable and that HβB2C may adopt a closed (completely folded) conformation, similar to the other members of the βγ-crystallin family. To corroborate this hypothesis, we performed extensive molecular dynamics simulations of HβB2C in its monomeric and dimeric conformations, using all-atom and coarse-grained scales. We employed Markov state model (MSM) analysis to characterize the conformational and kinetically relevant states in the folding process of monomeric HβB2C. The MSM analysis clearly shows that HβB2C adopts a completely folded structure, and this conformation is the most kinetically and energetically favourable one. In contrast, the extended conformations are kinetically unstable and energetically unfavourable. Our MSM analysis also reveals a key metastable state, which is particularly interesting because it is from this state that the folded state is reached. The folded state is stabilized by the formation of two salt bridges between the residue-pairs E74-R187 and R97-E166 and the two hydrophobic residue-pairs V59-L164 and V72-V151. Furthermore, free energy surface (FES) analysis revealed that the HβB2C dimer with both monomers in a closed conformation (face-en-face dimer) is energetically more stable than the domain-swapped dimer (crystallographic structure). The results presented in this report shed light on the molecular details of the folding mechanism of HβB2C in an aqueous environment and may contribute to interpreting different experimental findings. Finally, a detailed knowledge of HβB2C folding may be key to the rational design of potential molecules to treat cataract disease.
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Affiliation(s)
- José-Luis Velasco-Bolom
- Facultad de Química, Departamento de Fisicoquímica, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico.
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3
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Krishnan B, Srivastava SS, Sankeshi V, Garg R, Srivastava S, Sankaranarayanan R, Sharma Y. βγ-Crystallination Endows a Novel Bacterial Glycoside Hydrolase 64 with Ca 2+-Dependent Activity Modulation. J Bacteriol 2019; 201:e00392-19. [PMID: 31527113 PMCID: PMC6832075 DOI: 10.1128/jb.00392-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 09/05/2019] [Indexed: 01/10/2023] Open
Abstract
The prokaryotic βγ-crystallins are a large group of uncharacterized domains with Ca2+-binding motifs. We have observed that a vast number of these domains are found appended to other domains, in particular, the carbohydrate-active enzyme (CAZy) domains. To elucidate the functional significance of these prospective Ca2+ sensors in bacteria and this widespread domain association, we have studied one typical example from Clostridium beijerinckii, a bacterium known for its ability to produce acetone, butanol, and ethanol through fermentation of several carbohydrates. This novel glycoside hydrolase of family 64 (GH64), which we named glucanallin, is composed of a βγ-crystallin domain, a GH64 domain, and a carbohydrate-binding module 56 (CBM56). The substrates of GH64, β-1,3-glucans, are the targets for industrial biofuel production due to their plenitude. We have examined the Ca2+-binding properties of this protein, assayed its enzymatic activity, and analyzed the structural features of the β-1,3-glucanase domain through its high-resolution crystal structure. The reaction products resulting from the enzyme reaction of glucanallin reinforce the mixed nature of GH64 enzymes, in contrast to the prevailing notion of them being an exotype. Upon disabling Ca2+ binding and comparing different domain combinations, we demonstrate that the βγ-crystallin domain in glucanallin acts as a Ca2+ sensor and enhances the glycolytic activity of glucanallin through Ca2+ binding. We also compare the structural peculiarities of this new member of the GH64 family to two previously studied members.IMPORTANCE We have biochemically and structurally characterized a novel glucanase from the less studied GH64 family in a bacterium significant for fermentation of carbohydrates into biofuels. This enzyme displays a peculiar property of being distally modulated by Ca2+ via assistance from a neighboring βγ-crystallin domain, likely through changes in the domain interface. In addition, this enzyme is found to be optimized for functioning in an acidic environment, which is in line with the possibility of its involvement in biofuel production. Multiple occurrences of a similar domain architecture suggest that such a "βγ-crystallination"-mediated Ca2+ sensitivity may be widespread among bacterial proteins.
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Affiliation(s)
- Bal Krishnan
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
- Indian Institute of Science Education and Research Berhampur, Odisha, India
| | | | - Venu Sankeshi
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
| | - Rupsi Garg
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
| | | | | | - Yogendra Sharma
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
- Indian Institute of Science Education and Research Berhampur, Odisha, India
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4
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Roskamp KW, Kozlyuk N, Sengupta S, Bierma JC, Martin RW. Divalent Cations and the Divergence of βγ-Crystallin Function. Biochemistry 2019; 58:4505-4518. [PMID: 31647219 DOI: 10.1021/acs.biochem.9b00507] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The βγ-crystallin superfamily contains both β- and γ-crystallins of the vertebrate eye lens and the microbial calcium-binding proteins, all of which are characterized by a common double-Greek key domain structure. The vertebrate βγ-crystallins are long-lived structural proteins that refract light onto the retina. In contrast, the microbial βγ-crystallins bind calcium ions. The βγ-crystallin from the tunicate Ciona intestinalis (Ci-βγ) provides a potential link between these two functions. It binds calcium with high affinity and is found in a light-sensitive sensory organ that is highly enriched in metal ions. Thus, Ci-βγ is valuable for investigating the evolution of the βγ-crystallin fold away from calcium binding and toward stability in the apo form as part of the vertebrate lens. Here, we investigate the effect of Ca2+ and other divalent cations on the stability and aggregation propensity of Ci-βγ and human γS-crystallin (HγS). Beyond Ca2+, Ci-βγ is capable of coordinating Mg2+, Sr2+, Co2+, Mn2+, Ni2+, and Zn2+, although only Sr2+ is bound with comparable affinity to its preferred metal ion. The extent to which the tested divalent cations stabilize Ci-βγ structure correlates strongly with ionic radius. In contrast, none of the tested divalent cations improved the stability of HγS, and some of them induced aggregation. Zn2+, Ni2+, and Co2+ induce aggregation by interacting with cysteine residues, whereas Cu2+-mediated aggregation proceeds via a different binding site.
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Affiliation(s)
- Kyle W Roskamp
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States
| | - Natalia Kozlyuk
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States
| | - Suvrajit Sengupta
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States
| | - Jan C Bierma
- Department of Molecular Biology and Biochemistry , University of California , Irvine , California 92697-3900 , United States
| | - Rachel W Martin
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States.,Department of Molecular Biology and Biochemistry , University of California , Irvine , California 92697-3900 , United States
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5
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Structural studies on the individual domains of human γS-crystallin and its G57W mutant unfolds mechanistic insights into childhood cataracts. Biochem Biophys Res Commun 2019; 517:499-506. [DOI: 10.1016/j.bbrc.2019.07.094] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 07/24/2019] [Indexed: 01/21/2023]
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6
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Abundant Perithecial Protein (APP) from Neurospora is a primitive functional analog of ocular crystallins. Biochem Biophys Res Commun 2019; 516:796-800. [PMID: 31255285 DOI: 10.1016/j.bbrc.2019.06.102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 06/18/2019] [Indexed: 11/21/2022]
Abstract
The eye arose during the Cambrian explosion from pre-existing proteins that would have been recruited for the formation of the specialized components of this organ, such as the transparent lens. Proteins suitable for the role of lens crystallins would need to possess unusual physical properties and the study of such earliest analogs of ocular crystallins would add to our understanding of the nature of recruitment of proteins as lens/corneal crystallins. We show that the Abundant Perithecial Protein (APP) of the fungi Neurospora and Sordaria fulfils the criteria for an early crystallin analog. The perithecia in these fungal species are phototropic, and APP accumulates at a high concentration in the neck of the pitcher-shaped perithecium. Spores are formed at the base of the perithecium, and light contributes to their maturation. The hydrodynamic properties of APP appear to exclude dimer formation or aggregation at high protein concentrations. APP is also deficient in Ca2+ binding, a property seen in its close homolog, the calcium-binding cell adhesion molecule (DdCAD-1) from Dictyostelium discoidum. Comparable to crystallins, APP occurs in high concentrations and seems to have dispensed with Ca2+ binding in exchange for greater stability. These crystallin-like attributes of APP lead us to demonstrate that it is a primitive form of ocular crystallins.
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7
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Patel S, Krishnan B, Hosur RV, Chary KVR. Mechanistic Insights from Replica Exchange Molecular Dynamics Simulations into Mutation Induced Disordered-to-Ordered Transition in Hahellin, a βγ-Crystallin. J Phys Chem B 2019; 123:5086-5098. [DOI: 10.1021/acs.jpcb.9b03845] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Sunita Patel
- UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Mumbai 400098, India
- Tata Institute of Fundamental Research, Hyderabad 500107, India
| | - Bal Krishnan
- Indian Institute of Science Education and Research, Berhampur, 760010, India
| | - Ramakrishna V. Hosur
- UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Mumbai 400098, India
- Tata Institute of Fundamental Research, Mumbai 400005, India
| | - Kandala V. R. Chary
- Tata Institute of Fundamental Research, Hyderabad 500107, India
- Tata Institute of Fundamental Research, Mumbai 400005, India
- Indian Institute of Science Education and Research, Berhampur, 760010, India
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8
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On identifying low energy conformational excited states with differential ruggedness in human γS-crystallin promoting severe infantile cataracts. Biochem Biophys Res Commun 2019; 514:946-952. [PMID: 31092325 DOI: 10.1016/j.bbrc.2019.05.071] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 05/08/2019] [Indexed: 01/18/2023]
Abstract
Transient excited states in proteins can be accurately probed from temperature dependence of amide proton (1HN) chemical shifts displaying significant curvatures. Characterizing these near-native alternative states is of high therapeutic relevance in conformational diseases wherein missense mutations promote structural instability that leads to conformational heterogeneity. Extending the structure-function paradigm from physiology to pathology, we recently reported the solution NMR structure and dynamics of a severe congenital cataract variant, G57W of human γS-crystallin (abbreviated as γS-G57W) which is resistant towards crystallization. In an endeavour to explore the functional consequences of this mutation, here we report for the first time, native state conformational ruggedness in human γS-G57W as compared to its wild-type counterpart from residue resolved nonlinear temperature dependence of backbone 1HN chemical shifts using solution NMR spectroscopy. Our calculations suggest that the simulated chemical shift curvatures are indicative of low energy excited states within 2-4 kcal mol-1 from the native state. Residues accessing alternative conformations populate the N-terminal domain of γS-G57W more than its C-terminal counterpart. Collectively, curvatures retaining native state ensemble on mild denaturation suggest that the free energy landscape in human γS-G57W at the bottom of the folding funnel is sufficiently robust and malleable against such perturbations. Overall, this critical study highlights the functional aspects of such structural malleability promoting infantile cataracts as a global health risk marker.
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9
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Bari KJ, Sharma S, Chary KVR. Structural and functional characterization of a missense mutant of human γS-crystallin associated with dominant infantile cataracts. Biochem Biophys Res Commun 2018; 506:862-867. [PMID: 30391002 DOI: 10.1016/j.bbrc.2018.10.187] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 10/29/2018] [Indexed: 01/19/2023]
Abstract
Infantile cataracts constitute one of the most important causes of childhood blindness worldwide. Human γS-crystallin is the most abundant protein in the eye lens cortex. A missense mutant of human γS-crystallin, Y67N (abbreviated hereafter as γS-Y67N) is recently reported to be associated with dominant infantile cataracts. To understand the structural basis for γS-Y67N to cause lens opacification, we constructed, expressed and purified γS-Y67N and its wild-type (abbreviated hereafter as γS-WT) and studied the structural and functional differences between them in solution using circular dichroism (CD), differential scanning calorimetry (DSC), fluorescence spectroscopy and extrinsic spectral probes. Extensive equilibrium characterization indicate that replacement of the highly conserved Tyr at 67th position by Asn distorts the conserved Tyr corner at the second Greek key motif in the N-terminal domain (NTD) and leads to substantial loss of structural stability. Our intrinsic fluorescence quenching results reveal differential in-vitro refolding kinetics identifying partially folded kinetic intermediates for both proteins. Extrinsic fluorescence studies further reveal loosening up of the compact structure of γS-crystallin upon mutation associated with enhanced aggregation. As Ca2+ homeostasis is a crucial regulator of lens transparency, we further investigated the Ca2+-binding properties of γS-WT and γS-Y67N by isothermal titration calorimetry (ITC) to identify lens Ca2+ distribution in health and in disease. Overall, our results highlight the vital role of conserved Tyr corners in stabilizing Greek key motifs and provide useful structural and functional insights into the mechanism of cataract formation in humans.
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Affiliation(s)
- Khandekar Jishan Bari
- Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Gopanpally, Hyderabad, 500107, India
| | - Shrikant Sharma
- Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Gopanpally, Hyderabad, 500107, India
| | - Kandala V R Chary
- Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Gopanpally, Hyderabad, 500107, India; Department of Chemical Sciences, Tata Institute of Fundamental Research, 1, Homi Bhabha Road, Colaba, Mumbai, 400005, India; Indian Institute of Science Education and Research, Berhampur, Odisha, 760010, India.
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10
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Swaroop Srivastava S, Raman R, Kiran U, Garg R, Chadalawada S, Pawar AD, Sankaranarayanan R, Sharma Y. Interface interactions between βγ-crystallin domain and Ig-like domain render Ca 2+ -binding site inoperative in abundant perithecial protein of Neurospora crassa. Mol Microbiol 2018; 110:955-972. [PMID: 30216631 DOI: 10.1111/mmi.14130] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2018] [Indexed: 11/30/2022]
Abstract
We describe a set of proteins in which a βγ-crystallin domain pairs with an Ig-like domain, and which are confined to microbes, like bacteria, slime molds and fungi. DdCAD-1 (Ca2+ -dependent cell adhesion molecule-1) and abundant perithecial protein (APP) represent this class of molecules. Using the crystal structure of APP-NTD (N-terminal domain of APP), we describe its mode of Ca2+ binding and provide a generalized theme for correct identification of the Ca2+ -binding site within this class of molecules. As a common feature, one of the two Ca2+ -binding sites is non-functional in the βγ-crystallin domains of these proteins. While APP-NTD binds Ca2+ with a micromolar affinity which is comparable to DdCAD-1, APP surprisingly does not bind Ca2+ . Crystal structures of APP and Ca2+ -bound APP-NTD reveal that the interface interactions in APP render its Ca2+ -binding site inoperative. Thus, heterodomain association provides a novel mode of Ca2+ -binding regulation in APP. Breaking the interface interactions (mutating Asp30Ala, Leu132Ala and Ile135Ala) or separation from the Ig-like domain removes the constraints upon the required conformational transition and enables the βγ-crystallin domain to bind Ca2+ . In mechanistic detail, our work demonstrates an interdomain interface adapted to distinct functional niches in APP and its homolog DdCAD-1.
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Affiliation(s)
| | - Rajeev Raman
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Hyderabad, 500 007, India
| | - Uday Kiran
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Hyderabad, 500 007, India
| | - Rupsi Garg
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Hyderabad, 500 007, India
| | - Swathi Chadalawada
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Hyderabad, 500 007, India
| | - Asmita D Pawar
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Hyderabad, 500 007, India
| | - Rajan Sankaranarayanan
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Hyderabad, 500 007, India.,Academy of Scientific and Innovative Research (AcSIR), New Delhi, India
| | - Yogendra Sharma
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Hyderabad, 500 007, India.,Academy of Scientific and Innovative Research (AcSIR), New Delhi, India
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11
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Cerminati S, Paoletti L, Peirú S, Menzella HG, Castelli ME. The βγ-crystallin domain of Lysinibacillus sphaericus phosphatidylinositol phospholipase C plays a central role in protein stability. Appl Microbiol Biotechnol 2018; 102:6997-7005. [DOI: 10.1007/s00253-018-9136-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 04/25/2018] [Accepted: 05/23/2018] [Indexed: 10/14/2022]
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12
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Srivastava SS, Jamkhindikar AA, Raman R, Jobby MK, Chadalawada S, Sankaranarayanan R, Sharma Y. A Transition Metal-Binding, Trimeric βγ-Crystallin from Methane-Producing Thermophilic Archaea, Methanosaeta thermophila. Biochemistry 2017; 56:1299-1310. [DOI: 10.1021/acs.biochem.6b00985] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | - Rajeev Raman
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Maroor K. Jobby
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Swathi Chadalawada
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Rajan Sankaranarayanan
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Yogendra Sharma
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
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13
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Kozlyuk N, Sengupta S, Bierma JC, Martin RW. Calcium Binding Dramatically Stabilizes an Ancestral Crystallin Fold in Tunicate βγ-Crystallin. Biochemistry 2016; 55:6961-6968. [PMID: 27992995 DOI: 10.1021/acs.biochem.6b00937] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The tunicate (Ciona intestinalis) βγ-crystallin represents an intermediate case between the calcium-binding proteins ancestral to the vertebrate βγ-crystallin fold and the vertebrate structural crystallins. Unlike the structural βγ-crystallins in the vertebrate eye lens, this βγ-crystallin strongly binds Ca2+. Furthermore, Ca2+ binding greatly stabilizes the protein, an effect that has previously been observed in microbial βγ-crystallins but not in those of vertebrates. This relationship between binding and protein stabilization makes the tunicate βγ-crystallin an interesting model for studying the evolution of the human βγ-crystallin. We also compare and contrast the binding sites of tunicate βγ-crystallin with those of other βγ-crystallins to develop hypotheses about the functional origin of the lack of Ca2+-binding sites in human crystallins.
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Affiliation(s)
- Natalia Kozlyuk
- Department of Chemistry, University of California , Irvine, California 92697-2025, United States
| | - Suvrajit Sengupta
- Department of Chemistry, University of California , Irvine, California 92697-2025, United States
| | - Jan C Bierma
- Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697-3900, United States
| | - Rachel W Martin
- Department of Chemistry, University of California , Irvine, California 92697-2025, United States.,Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697-3900, United States
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14
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Hartwich H, Rosengauer E, Rüttiger L, Wilms V, Waterholter SK, Nothwang HG. Functional Role of γ-Crystallin N in the Auditory Hindbrain. PLoS One 2016; 11:e0161140. [PMID: 27517863 PMCID: PMC4982622 DOI: 10.1371/journal.pone.0161140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 07/30/2016] [Indexed: 12/20/2022] Open
Abstract
γ-crystallins are major components of the vertebrate lens but show expression in other tissues as well. Their extralenticular functions remain so far unclear. Here, we explored such roles in the rodent superior olivary complex in which previous analysis demonstrated developmentally regulated expression of Crygd, Cryge and Crygn. Immunohistochemistry with novel antibodies against Crygd/e and Crygn indicate that expression of Crygd/e was moderate and varied between the perinatal superior olivary complex of mice, rats, and gerbils. Crygn-immunoreactivity was more robust and consistently highest in the medial nucleus of the trapezoid body, but also present in other nuclei of the superior olivary complex. To analyze the function of Crygn in the auditory hindbrain, we used a Crygn allele with a floxed exon 2. Upon pairing with Egr2::Cre mice, exon 2, encoding the first two greek key motifs of Crygn, was deleted in the developing auditory hindbrain. Anatomical analysis of these mice revealed a 20% volume reduction in the medial nucleus of the trapezoid body and a 7% reduction in the lateral superior olive at postnatal day 25. This was due to cell loss between postnatal days 4 and 25, whereas cell size was unaffected. Auditory brainstem responses showed normal threshold but a significant increase in the amplitude of wave IV. Crygn is hence required for postmigratory survival and proper function of auditory hindbrain neurons. These results ascertain for the first time an essential extralenticular role for γ-crystallins in vivo.
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Affiliation(s)
- Heiner Hartwich
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Elena Rosengauer
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Lukas Rüttiger
- University of Tübingen, Department of Otolaryngology, Hearing Research Centre Tübingen (THRC), Molecular Physiology of Hearing, Elfriede Aulhorn Str. 5, 72076, Tübingen, Germany
| | - Viviane Wilms
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Sarah-Kristin Waterholter
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Hans Gerd Nothwang
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- * E-mail:
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15
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Scholl ZN, Li Q, Yang W, Marszalek PE. Single-molecule Force Spectroscopy Reveals the Calcium Dependence of the Alternative Conformations in the Native State of a βγ-Crystallin Protein. J Biol Chem 2016; 291:18263-75. [PMID: 27378818 DOI: 10.1074/jbc.m116.729525] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Indexed: 12/30/2022] Open
Abstract
Although multidomain proteins predominate the proteome of all organisms and are expected to display complex folding behaviors and significantly greater structural dynamics as compared with single-domain proteins, their conformational heterogeneity and its impact on their interaction with ligands are poorly understood due to a lack of experimental techniques. The multidomain calcium-binding βγ-crystallin proteins are particularly important because their deterioration and misfolding/aggregation are associated with melanoma tumors and cataracts. Here we investigate the mechanical stability and conformational dynamics of a model calcium-binding βγ-crystallin protein, Protein S, and elaborate on its interactions with calcium. We ask whether domain interactions and calcium binding affect Protein S folding and potential structural heterogeneity. Our results from single-molecule force spectroscopy show that the N-terminal (but not the C-terminal) domain is in equilibrium with an alternative conformation in the absence of Ca(2+), which is mechanically stable in contrast to other proteins that were observed to sample a molten globule under similar conditions. Mutagenesis experiments and computer simulations reveal that the alternative conformation of the N-terminal domain is caused by structural instability produced by the high charge density of a calcium binding site. We find that this alternative conformation in the N-terminal domain is diminished in the presence of calcium and can also be partially eliminated with a hitherto unrecognized compensatory mechanism that uses the interaction of the C-terminal domain to neutralize the electronegative site. We find that up to 1% of all identified multidomain calcium-binding proteins contain a similarly highly charged site and therefore may exploit a similar compensatory mechanism to prevent structural instability in the absence of ligand.
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Affiliation(s)
| | - Qing Li
- the Department of Mechanical Engineering and Materials Science, and
| | - Weitao Yang
- the Department of Chemistry, Duke University, Durham, North Carolina 27708
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Mishra A, Krishnan B, Raman R, Sharma Y. Ca2+ and βγ-crystallins: An affair that did not last? Biochim Biophys Acta Gen Subj 2015; 1860:299-303. [PMID: 26145580 DOI: 10.1016/j.bbagen.2015.06.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 06/25/2015] [Accepted: 06/29/2015] [Indexed: 12/15/2022]
Abstract
BACKGROUND During the last three decades, lens β- and γ-crystallins have found a huge number of kin from numerous taxonomical sources. Most of these proteins from invertebrates and microbes have been demonstrated or predicted to bind Ca2+ involving a distinct double-clamp motif, which is largely degenerated in lens homologues. SCOPE OF REVIEW The various aspects of transformation of βγ-crystallins from a quintessential Ca2+-binding protein into a primarily structural molecule have been reviewed. MAJOR CONCLUSIONS In lens members of βγ-crystallins, the residues involved in Ca2+ binding have diverged considerably from the classical consensus with consequent reduction in their Ca2+-binding properties. This evolutionary change is congenial to their new role as robust constituents of lens. The exact functions of the residual affinity for Ca2+ are yet to be established. GENERAL SIGNIFICANCE This review highlights the significance of reduction in Ca2+-binding ability of the βγ-crystallins for lens physiology and why this residual affinity may be functionally important. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Amita Mishra
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Bal Krishnan
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Rajeev Raman
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Yogendra Sharma
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India.
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Slingsby C, Wistow GJ. Functions of crystallins in and out of lens: roles in elongated and post-mitotic cells. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:52-67. [PMID: 24582830 PMCID: PMC4104235 DOI: 10.1016/j.pbiomolbio.2014.02.006] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Accepted: 02/18/2014] [Indexed: 12/25/2022]
Abstract
The vertebrate lens evolved to collect light and focus it onto the retina. In development, the lens grows through massive elongation of epithelial cells possibly recapitulating the evolutionary origins of the lens. The refractive index of the lens is largely dependent on high concentrations of soluble proteins called crystallins. All vertebrate lenses share a common set of crystallins from two superfamilies (although other lineage specific crystallins exist). The α-crystallins are small heat shock proteins while the β- and γ-crystallins belong to a superfamily that contains structural proteins of uncertain function. The crystallins are expressed at very high levels in lens but are also found at lower levels in other cells, particularly in retina and brain. All these proteins have plausible connections to maintenance of cytoplasmic order and chaperoning of the complex molecular machines involved in the architecture and function of cells, particularly elongated and post-mitotic cells. They may represent a suite of proteins that help maintain homeostasis in such cells that are at risk from stress or from the accumulated insults of aging.
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Affiliation(s)
- Christine Slingsby
- Department of Biological Sciences, Crystallography, Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK.
| | - Graeme J Wistow
- Section on Molecular Structure and Functional Genomics, National Eye Institute, Bg 6, Rm 106, National Institutes of Health, Bethesda, MD 20892-0608, USA
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18
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Mishra A, Krishnan B, Srivastava SS, Sharma Y. Microbial βγ-crystallins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:42-51. [PMID: 24594023 DOI: 10.1016/j.pbiomolbio.2014.02.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Revised: 02/18/2014] [Accepted: 02/20/2014] [Indexed: 01/24/2023]
Abstract
βγ-Crystallins have emerged as a superfamily of structurally homologous proteins with representatives across the domains of life. A major portion of this superfamily is constituted by members from microorganisms. This superfamily has also been recognized as a novel group of Ca(2+)-binding proteins with huge diversity. The βγ domain shows variable properties in Ca(2+) binding, stability and association with other domains. The various members present a series of evolutionary adaptations culminating in great diversity in properties and functions. Most of the predicted βγ-crystallins are yet to be characterized experimentally. In this review, we outline the distinctive features of microbial βγ-crystallins and their position in the βγ-crystallin superfamily.
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Affiliation(s)
- Amita Mishra
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Bal Krishnan
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | | | - Yogendra Sharma
- CSIR - Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India.
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19
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Srivastava SS, Mishra A, Krishnan B, Sharma Y. Ca2+-binding motif of βγ-crystallins. J Biol Chem 2014; 289:10958-10966. [PMID: 24567326 DOI: 10.1074/jbc.o113.539569] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
βγ-Crystallin-type double clamp (N/D)(N/D)XX(S/T)S motif is an established but sparsely investigated motif for Ca(2+) binding. A βγ-crystallin domain is formed of two Greek key motifs, accommodating two Ca(2+)-binding sites. βγ-Crystallins make a separate class of Ca(2+)-binding proteins (CaBP), apparently a major group of CaBP in bacteria. Paralleling the diversity in βγ-crystallin domains, these motifs also show great diversity, both in structure and in function. Although the expression of some of them has been associated with stress, virulence, and adhesion, the functional implications of Ca(2+) binding to βγ-crystallins in mediating biological processes are yet to be elucidated.
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Affiliation(s)
- Shanti Swaroop Srivastava
- Centre for Cellular and Molecular Biology (CCMB), Council of Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad-500 007, India
| | - Amita Mishra
- Centre for Cellular and Molecular Biology (CCMB), Council of Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad-500 007, India
| | - Bal Krishnan
- Centre for Cellular and Molecular Biology (CCMB), Council of Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad-500 007, India
| | - Yogendra Sharma
- Centre for Cellular and Molecular Biology (CCMB), Council of Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad-500 007, India.
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20
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Rose SL, Fulton JM, Brown CM, Natale F, Van Mooy BAS, Bidle KD. Isolation and characterization of lipid rafts inEmiliania huxleyi: a role for membrane microdomains in host-virus interactions. Environ Microbiol 2014; 16:1150-66. [DOI: 10.1111/1462-2920.12357] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 12/05/2013] [Indexed: 01/21/2023]
Affiliation(s)
- Suzanne L. Rose
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
| | - James M. Fulton
- Department of Marine Chemistry and Geochemistry; Woods Hole Oceanographic Institution; Woods Hole MA USA
| | - Christopher M. Brown
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
| | - Frank Natale
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
| | - Benjamin A. S. Van Mooy
- Department of Marine Chemistry and Geochemistry; Woods Hole Oceanographic Institution; Woods Hole MA USA
| | - Kay D. Bidle
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
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21
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Patel S, Ramanujam V, Srivastava AK, Chary KVR. Conformational propensities and dynamics of a βγ-crystallin, an intrinsically disordered protein. Phys Chem Chem Phys 2014; 16:12703-18. [DOI: 10.1039/c3cp53558d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Suman SK, Mishra A, Yeramala L, Rastogi ID, Sharma Y. Disability for function: loss of Ca(2+)-binding is obligatory for fitness of mammalian βγ-crystallins. Biochemistry 2013; 52:9047-58. [PMID: 24251594 DOI: 10.1021/bi401093n] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vertebrate βγ-crystallins belonging to the βγ-crystallin superfamily lack functional Ca(2+)-binding sites, while their microbial homologues do not; for example, three out of four sites in lens γ-crystallins are disabled. Such loss of Ca(2+)-binding function in non-lens βγ-crystallins from mammals (e.g., AIM1 and Crybg3) raises the possibility of a trade-off in the evolutionary extinction of Ca(2+)-binding. We test this hypothesis by reconstructing ancestral Ca(2+)-binding motifs (transforming disabled motifs into the canonical ones) in the lens γB-crystallin by introducing minimal sets of mutations. Upon incorporation of serine at the fifth position in the N/D-N/D-X-X-S/T(5)-S motif, which endowed a domain with microbial characteristics, a decreased domain stability was observed. Ca(2+) further destabilized the N-terminal domain (NTD) and its serine mutants profoundly, while the incorporation of a C-terminal domain (CTD) nullified this destabilization. On the other hand, Ca(2+)-induced destabilization of the CTD was not rescued by the introduction of an NTD. Of note, only one out of four sites is functional in the NTD of γB-crystallins responsible for weak Ca(2+) binding, but the deleterious effects of Ca(2+) are overcome by introduction of a CTD. The rationale for the onset of cataracts by certain mutations, such as R77S, which have not been clarified by structural means, could be explained by this work. The findings presented here shed light on the evolutionary innovations in terms of the functional loss of Ca(2+)-binding and acquisition of a bilobed domain, besides imparting additional advantages (e.g., protection from light) required for specialized functions.
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Affiliation(s)
- Shashi Kumar Suman
- Centre for Cellular and Molecular Biology (CCMB), CSIR , Uppal Road, Hyderabad 500007, India
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23
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Ramanujam V, Patel S, Srivastava AK, Sharma Y, Chary KVR. Backbone ¹H, ¹³C and ¹⁵N resonance assignments of an intrinsically unstructured βγ-crystallin from Hahella chejuensis. BIOMOLECULAR NMR ASSIGNMENTS 2013; 7:221-224. [PMID: 22836948 DOI: 10.1007/s12104-012-9414-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 07/16/2012] [Indexed: 06/01/2023]
Abstract
The sequence specific backbone (1)H, (13)C and (15)N resonance assignments of an intrinsically unstructured βγ-crystallin from Hahella chejuensis are reported. The secondary structure chracterization of the unstructured protein reveals that large fraction of residues exhibits β-strand propensity, as in the case of the Ca(2+)-bound structured protein.
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Affiliation(s)
- Venkatraman Ramanujam
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
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Johnson AC, Lee JW, Harmon AC, Morris Z, Wang X, Fratkin J, Rapp JP, Gomez-Sanchez E, Garrett MR. A mutation in the start codon of γ-crystallin D leads to nuclear cataracts in the Dahl SS/Jr-Ctr strain. Mamm Genome 2013; 24:95-104. [PMID: 23404175 PMCID: PMC3628938 DOI: 10.1007/s00335-013-9447-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 12/17/2012] [Indexed: 10/27/2022]
Abstract
Cataracts are a major cause of blindness. The most common forms of cataracts are age- and UV-related and develop mostly in the elderly, while congenital cataracts appear at birth or in early childhood. The Dahl salt-sensitive (SS/Jr) rat is an extensively used model of salt-sensitive hypertension that exhibits concomitant renal disease. In the mid-1980s, cataracts appeared in a few animals in the Dahl S colony, presumably the result of a spontaneous mutation. The mutation was fixed and bred to establish the SS/Jr-Ctr substrain. The SS/Jr-Ctr substrain has been used exclusively by a single investigator to study the role of steroids and hypertension. Using a classical positional cloning approach, we localized the cataract gene with high resolution to a less than 1-Mbp region on chromosome 9 using an F1(SS/Jr-Ctr × SHR) × SHR backcross population. The 1-Mbp region contained only 13 genes, including 4 genes from the γ-crystallins (Cryg) gene family, which are known to play a role in cataract formation. All of the γ-crystallins were sequenced and a novel point mutation in the start codon (ATG → GTG) of the Crygd gene was identified. This led to the complete absence of the CRYGD protein in the eyes of the SS/Jr-Ctr strain. In summary, the identification of the genetic cause in this novel cataract model may provide an opportunity to better understand the development of cataracts, particularly in the context of hypertension.
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Affiliation(s)
- Ashley C. Johnson
- Department of Pharmacology, University of Mississippi Medical Center, Jackson, MS 39216
| | - Jonathan W. Lee
- Department of Pharmacology, University of Mississippi Medical Center, Jackson, MS 39216
| | - Ashlyn C. Harmon
- Department of Pharmacology, University of Mississippi Medical Center, Jackson, MS 39216
| | - Zaliya Morris
- Department of Pharmacology, University of Mississippi Medical Center, Jackson, MS 39216
| | - Xuexiang Wang
- Department of Pharmacology, University of Mississippi Medical Center, Jackson, MS 39216
| | - Jonathan Fratkin
- Department of Pathology, University of Mississippi Medical Center, Jackson, MS 39216
| | | | - Elise Gomez-Sanchez
- Department of Pharmacology, University of Mississippi Medical Center, Jackson, MS 39216
- GV(Sonny) Montgomery VAMC
| | - Michael R. Garrett
- Department of Pharmacology, University of Mississippi Medical Center, Jackson, MS 39216
- Department of Medicine (Nephrology), University of Mississippi Medical Center, Jackson, MS 39216
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Suman SK, Ravindra D, Sharma Y, Mishra A. Association properties and unfolding of a βγ-crystallin domain of a Vibrio-specific protein. PLoS One 2013; 8:e53610. [PMID: 23349723 PMCID: PMC3551895 DOI: 10.1371/journal.pone.0053610] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 12/03/2012] [Indexed: 11/19/2022] Open
Abstract
The βγ-crystallin superfamily possesses a large number of versatile members, of which only a few members other than lens βγ-crystallins have been studied. Understanding the non-crystallin functions as well as origin of crystallin-like properties of such proteins is possible by exploring novel members from diverse sources. We describe a novel βγ-crystallin domain with S-type (Spherulin 3a type) Greek key motifs in protein vibrillin from a pathogenic bacterium Vibrio cholerae. This domain is a part of a large Vibrio-specific protein prevalent in Vibrio species (found in at least fourteen different strains sequenced so far). The domain contains two canonical N/D-N/D-X-X-S/T-S Ca2+-binding motifs, and bind Ca2+. Unlike spherulin 3a and other microbial homologues studied so far, βγ-crystallin domain of vibrillin self-associates forming oligomers of various sizes including dimers. The fractionated dimers readily form octamers in concentration-dependent manner, suggesting an association between these two major forms. The domain associates/dissociates forming dimers at the cost of monomeric populations in the presence of Ca2+. No such effect of Ca2+ has been observed in oligomeric species. The equilibrium unfolding of both forms follows a similar pattern, with the formation of an unfolding intermediate at sub-molar concentrations of denaturant. These properties exhibited by this βγ-crystallin domain are not shown by any other domain studied so far, demonstrating the diversity in domain properties.
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Affiliation(s)
- Shashi Kumar Suman
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad, India
| | - Daddali Ravindra
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad, India
| | - Yogendra Sharma
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad, India
- * E-mail: (YS); (AM)
| | - Amita Mishra
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad, India
- * E-mail: (YS); (AM)
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Vendra VPR, Chandani S, Balasubramanian D. The mutation V42M distorts the compact packing of the human gamma-S-crystallin molecule, resulting in congenital cataract. PLoS One 2012; 7:e51401. [PMID: 23284690 PMCID: PMC3528740 DOI: 10.1371/journal.pone.0051401] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 11/01/2012] [Indexed: 11/19/2022] Open
Abstract
Background Human γS-crystallin is an important component of the human eye lens nucleus and cortex. The mutation V42M in the molecule causes severe congenital cataract in children. We compare the structure of the mutant protein with that of the wild type in order to understand how structural changes in the mutant relate to the mechanism of opacification. Methods Both proteins were made using conventional cloning and expression procedures. Secondary and tertiary structural features of the proteins were analyzed using spectral methods. Structural stabilities of the proteins were analyzed using chemical and thermal denaturation methods. Self-aggregation was monitored using extrinsic spectral probes. Molecular modeling was used to compare the structural features of the two proteins. Results While the wild type and mutant have the same secondary structure, molecular modeling and fluorescence analysis suggest the mutant to have a more open tertiary structure, with a larger hydrophobic surface. Experiments using extrinsic probes reveal that the mutant readily self-aggregates, with the suggestion that the aggregates might be similar to amyloidogenic fibrils. Chemical denaturation indicates that while the wild type exhibits the classic two-state transition, V42M goes through an intermediate state, and has a distinctly lower stability than the wild type. The temperature of thermal unfolding of the mutant is also distinctly lower. Further, the mutant readily precipitates and scatters light more easily than the wild type. Conclusion The replacement of valine in position 42 by the longer and bulkier methionine in human γS-crystallin perturbs the compact β-sheet core packing topology in the N-terminal domain of the molecule, exposes nonpolar residues thereby increasing the surface hydrophobicity and weakens the stability of the protein, thus promoting self-aggregation leading to light scattering particles. This set of changes in the properties of the mutant offers a molecular insight into the mechanism of opacification.
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Affiliation(s)
- Venkata Pulla Rao Vendra
- Prof. Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, LV Prasad Eye Institute, Hyderabad, India
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Guanidine-HCl dependent structural unfolding of M-crystallin: fluctuating native state like topologies and intermolecular association. PLoS One 2012; 7:e42948. [PMID: 23284604 PMCID: PMC3524170 DOI: 10.1371/journal.pone.0042948] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 07/16/2012] [Indexed: 11/19/2022] Open
Abstract
Numerous experimental techniques and computational studies, proposed in recent times, have revolutionized the understanding of protein-folding paradigm. The complete understanding of protein folding and intermediates are of medical relevance, as the aggregation of misfolding proteins underlies various diseases, including some neurodegenerative disorders. Here, we describe the unfolding of M-crystallin, a βγ-crystallin homologue protein from archaea, from its native state to its denatured state using multidimensional NMR and other biophysical techniques. The protein, which was earlier characterized to be a predominantly β-sheet protein in its native state, shows different structural propensities (α and β), under different denaturing conditions. In 2 M GdmCl, the protein starts showing two distinct sets of peaks, with one arising from a partially unfolded state and the other from a completely folded state. The native secondary structural elements start disappearing as the denaturant concentration approaches 4 M. Subsequently, the protein is completely unfolded when the denaturant concentration is 6 M. The (15)N relaxation data (T(1)/T(2)), heteronuclear (1)H-(15)N Overhauser effects (nOes), NOESY data, and other biophysical data taken together indicate that the protein shows a consistent, gradual change in its structural and motional preferences with increasing GdmCl concentration.
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Rajanikanth V, Srivastava SS, Singh AK, Rajyalakshmi M, Chandra K, Aravind P, Sankaranarayanan R, Sharma Y. Aggregation-prone near-native intermediate formation during unfolding of a structurally similar nonlenticular βγ-crystallin domain. Biochemistry 2012; 51:8502-13. [PMID: 23043265 DOI: 10.1021/bi300844u] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The folding and unfolding of structurally similar proteins belonging to a family have long been a focus of investigation of the structure-(un)folding relationship. Such studies are yet to reach a consensus about whether structurally similar domains follow common or different unfolding pathways. Members of the βγ-crystallin superfamily, which consists of structurally similar proteins with limited sequence similarity from diverse life forms spanning microbes to mammals, form an appropriate model system for exploring this relationship further. We selected a new member, Crybg3_D3, the third βγ-crystallin domain of non-lens vertebrate protein Crybg3 from mouse brain. The crystal structure determined at 1.86 Å demonstrates that the βγ-crystallin domain of Crybg3 resembles more closely the lens βγ-crystallins than the microbial crystallins do. However, interestingly, this structural cousin follows a quite distinct (un)folding pathway via formation of an intermediate state. The intermediate species is in a nativelike conformation with variation in flexibility and tends to form insoluble aggregates. The individual domains of lens βγ-crystallins (and microbial homologues) do not follow such an unfolding pattern. Thus, even the closest members of a subfamily within a superfamily do not necessarily follow similar unfolding paths, suggesting the divergence acquired by these domains, which could be observed only by unfolding. Additionally, this study provides insights into the modifications that this domain has undergone during its recruitment into the non-lens tissues in vertebrates.
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Affiliation(s)
- V Rajanikanth
- Centre for Cellular and Molecular Biology (CCMB), Council of Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad 500 007, India
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