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Khadka NK, Hazen P, Haemmerle D, Mainali L. Interaction of β L- and γ-Crystallin with Phospholipid Membrane Using Atomic Force Microscopy. Int J Mol Sci 2023; 24:15720. [PMID: 37958704 PMCID: PMC10649403 DOI: 10.3390/ijms242115720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/26/2023] [Accepted: 10/27/2023] [Indexed: 11/15/2023] Open
Abstract
Highly concentrated lens proteins, mostly β- and γ-crystallin, are responsible for maintaining the structure and refractivity of the eye lens. However, with aging and cataract formation, β- and γ-crystallin are associated with the lens membrane or other lens proteins forming high-molecular-weight proteins, which further associate with the lens membrane, leading to light scattering and cataract development. The mechanism by which β- and γ-crystallin are associated with the lens membrane is unknown. This work aims to study the interaction of β- and γ-crystallin with the phospholipid membrane with and without cholesterol (Chol) with the overall goal of understanding the role of phospholipid and Chol in β- and γ-crystallin association with the membrane. Small unilamellar vesicles made of Chol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (Chol/POPC) membranes with varying Chol content were prepared using the rapid solvent exchange method followed by probe tip sonication and then dispensed on freshly cleaved mica disk to prepare a supported lipid membrane. The βL- and γ-crystallin from the cortex of the bovine lens was used to investigate the time-dependent association of βL- and γ-crystallin with the membrane by obtaining the topographical images using atomic force microscopy. Our study showed that βL-crystallin formed semi-transmembrane defects, whereas γ-crystallin formed transmembrane defects on the phospholipid membrane. The size of semi-transmembrane defects increases significantly with incubation time when βL-crystallin interacts with the membrane. In contrast, no significant increase in transmembrane defect size was observed in the case of γ-crystallin. Our result shows that Chol inhibits the formation of membrane defects when βL- and γ-crystallin interact with the Chol/POPC membrane, where the degree of inhibition depends upon the amount of Chol content in the membrane. At a Chol/POPC mixing ratio of 0.3, membrane defects were observed when both βL- and γ-crystallin interacted with the membrane. However, at a Chol/POPC mixing ratio of 1, no association of γ-crystallin with the membrane was observed, which resulted in a defect-free membrane, and the severity of the membrane defect was decreased when βL-crystallin interacted with the membrane. The semi-transmembrane or transmembrane defects formed by the interaction of βL- and γ-crystallin on phospholipid membrane might be responsible for light scattering and cataract formation. However, Chol suppressed the formation of such defects in the membrane, likely maintaining lens membrane homeostasis and protecting against cataract formation.
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Affiliation(s)
- Nawal K. Khadka
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (D.H.)
| | - Preston Hazen
- Biomolecular Sciences Graduate Program, Boise State University, Boise, ID 83725, USA;
| | - Dieter Haemmerle
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (D.H.)
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (D.H.)
- Biomolecular Sciences Graduate Program, Boise State University, Boise, ID 83725, USA;
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2
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Hazen P, Trossi-Torres G, Khadka NK, Timsina R, Mainali L. Binding of β L-Crystallin with Models of Animal and Human Eye Lens-Lipid Membrane. Int J Mol Sci 2023; 24:13600. [PMID: 37686406 PMCID: PMC10487507 DOI: 10.3390/ijms241713600] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 08/30/2023] [Accepted: 08/31/2023] [Indexed: 09/10/2023] Open
Abstract
Several discoveries show that with age and cataract formation, β-crystallin binds with the lens membrane or associates with other lens proteins, which bind with the fiber cell plasma membrane, accompanied by light scattering and cataract formation. However, how lipids (phospholipids and sphingolipids) and cholesterol (Chol) influence β-crystallin binding to the membrane is unclear. This research aims to elucidate the role of lipids and Chol in the binding of β-crystallin to the membrane and the membrane's physical properties (mobility, order, and hydrophobicity) with β-crystallin binding. We used electron paramagnetic resonance (EPR) spin-labeling methods to investigate the binding of βL-crystallin with a model of porcine lens-lipid (MPLL), model of mouse lens-lipid (MMLL), and model of human lens-lipid (MHLL) membrane with and without Chol. Our results show that βL-crystallin binds with all of the investigated membranes in a saturation manner, and the maximum parentage of the membrane surface occupied (MMSO) by βL-crystallin and the binding affinity (Ka) of βL-crystallin to the membranes followed trends: MMSO (MPLL) > MMSO (MMLL) > MMSO (MHLL) and Ka (MHLL) > Ka (MMLL) ≈ Ka (MPLL), respectively, in which the presence of Chol reduces the MMSO and Ka for all membranes. The mobility near the headgroup regions of the membranes decreases with an increase in the binding of βL-crystallin; however, the decrease is more pronounced in the MPLL and MMLL membranes than the MHLL membrane. In the MPLL and MMLL membranes, the membranes become slightly ordered near the headgroup with an increase in βL-crystallin binding compared to the MHLL membrane. The hydrophobicity near the headgroup region of the membrane increases with βL-crystallin binding; however, the increase is more pronounced in the MPLL and MMLL membranes than the MHLL membrane, indicating that βL-crystallin binding creates a hydrophobic barrier for the passage of polar molecules, which supports the barrier hypothesis in cataract formation. However, in the presence of Chol, there is no significant increase in hydrophobicity with βL-crystallin binding, suggesting that Chol prevents the formation of a hydrophobic barrier, possibly protecting against cataract formation.
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Affiliation(s)
- Preston Hazen
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.)
| | - Geraline Trossi-Torres
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.)
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
| | - Nawal K. Khadka
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
| | - Raju Timsina
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
| | - Laxman Mainali
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.)
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
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3
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Worth CL, Blundell TL. On the evolutionary conservation of hydrogen bonds made by buried polar amino acids: the hidden joists, braces and trusses of protein architecture. BMC Evol Biol 2010; 10:161. [PMID: 20513243 PMCID: PMC2892493 DOI: 10.1186/1471-2148-10-161] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Accepted: 05/31/2010] [Indexed: 11/10/2022] Open
Abstract
Background The hydrogen bond patterns between mainchain atoms in protein structures not only give rise to regular secondary structures but also satisfy mainchain hydrogen bond potential. However, not all mainchain atoms can be satisfied through hydrogen bond interactions that arise in regular secondary structures; in some locations sidechain-to-mainchain hydrogen bonds are required to provide polar group satisfaction. Buried polar residues that are hydrogen-bonded to mainchain amide atoms tend to be highly conserved within protein families, confirming that mainchain architecture is a critical restraint on the evolution of proteins. We have investigated the stabilizing roles of buried polar sidechains on the backbones of protein structures by performing an analysis of solvent inaccessible residues that are entirely conserved within protein families and superfamilies and hydrogen bonded to an equivalent mainchain atom in each family member. Results We show that polar and sometimes charged sidechains form hydrogen bonds to mainchain atoms in the cores of proteins in a manner that has been conserved in evolution. Although particular motifs have previously been identified where buried polar residues have conserved roles in stabilizing protein structure, for example in helix capping, we demonstrate that such interactions occur in a range of architectures and highlight those polar amino acid types that fulfil these roles. We show that these buried polar residues often span elements of secondary structure and provide stabilizing interactions of the overall protein architecture. Conclusions Conservation of buried polar residues and the hydrogen-bond interactions that they form implies an important role for maintaining protein structure, contributing strong restraints on amino acid substitutions during divergent protein evolution. Our analysis sheds light on the important stabilizing roles of these residues in protein architecture and provides further insight into factors influencing the evolution of protein families and superfamilies.
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Affiliation(s)
- Catherine L Worth
- Biocomputing Group, Biochemistry Department, University of Cambridge, Cambridge, CB2 1GA, UK
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4
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Structural and functional restraints in the evolution of protein families and superfamilies. Biochem Soc Trans 2009; 37:727-33. [DOI: 10.1042/bst0370727] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Divergent evolution of proteins reflects both selectively advantageous and neutral amino acid substitutions. In the present article, we examine restraints on sequence, which arise from selectively advantageous roles for structure and function and which lead to the conservation of local sequences and structures in families and superfamilies. We analyse structurally aligned members of protein families and superfamilies in order to investigate the importance of the local structural environment of amino acid residues in the acceptance of amino acid substitutions during protein evolution. We show that solvent accessibility is the most important determinant, followed by the existence of hydrogen bonds from the side-chain to main-chain functions and the nature of the element of secondary structure to which the amino acid contributes. Polar side chains whose hydrogen-bonding potential is satisfied tend to be more conserved than their unsatisfied or non-hydrogen-bonded counterparts, and buried and satisfied polar residues tend to be significantly more conserved than buried hydrophobic residues. Finally, we discuss the importance of functional restraints in the form of interactions of proteins with other macromolecules in assemblies or with substrates, ligands or allosteric regulators. We show that residues involved in such functional interactions are significantly more conserved and have differing amino acid substitution patterns.
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5
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Molecular cloning, sequence identification, and tissue expression profile analysis of three novel porcine genes: SDHB, SNRPA and CRYBB1. Mol Biol Rep 2008; 36:683-90. [DOI: 10.1007/s11033-008-9229-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2008] [Accepted: 03/10/2008] [Indexed: 10/22/2022]
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Garner B, Shaw DC, Lindner RA, Carver JA, Truscott RJ. Non-oxidative modification of lens crystallins by kynurenine: a novel post-translational protein modification with possible relevance to ageing and cataract. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1476:265-78. [PMID: 10669791 DOI: 10.1016/s0167-4838(99)00234-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In humans, the crystallin proteins of the ocular lens become yellow-coloured and fluorescent with ageing. With the development of senile nuclear cataract, the crystallins become brown and additional fluorophores are formed. The mechanism underlying crystallin colouration is not known but may involve interaction with kynurenine-derived UV filter compounds. We have recently identified a sulphur-linked glutathionyl-3-hydroxykynurenine glucoside adduct in the lens and speculated that kynurenine may also form adducts with GSH and possibly with nucleophilic amino acids of the crystallins (e.g. Cys). Here we show that kynurenine modifies calf lens crystallins non-oxidatively to yield coloured (365 nm absorbing), fluorescent (Ex 380 nm/Em 450-490 nm) protein adducts. Carboxymethylation and succinylation of crystallins inhibited kynurenine-mediated modification by approx. 90%, suggesting that Cys, Lys and possibly His residues may be involved. This was confirmed by showing that kynurenine formed adducts with GSH as well as with poly-His and poly-Lys. NMR studies revealed that the novel poly-Lys-kynurenine covalent linkage was via the epsilon-amino group of the Lys side chain and the betaC of the kynurenine side chain. Analysis of tryptic peptides of kynurenine-modified crystallins revealed that all of the coloured peptides contained either His, Cys or an internal Lys residue. We propose a novel mechanism of kynurenine-mediated crystallin modification which does not require UV light or oxidative conditions as catalysts. Rather, we suggest that the side chain of kynurenine-derived lens UV filters becomes deaminated to yield an alpha,beta-unsaturated carbonyl which is highly susceptible to attack by nucleophilic amino acid residues of the crystallins. The inability of the lens fibre cells to metabolise their constituent proteins results in the accumulation of coloured/fluorescent crystallins with age.
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Affiliation(s)
- B Garner
- Australian Cataract Research Foundation, University of Wollongong, Wollongong, NSW, Australia.
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7
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Srivastava OP, Srivastava K, Harrington V. Age-related degradation of betaA3/A1-crystallin in human lenses. Biochem Biophys Res Commun 1999; 258:632-8. [PMID: 10329436 DOI: 10.1006/bbrc.1999.0506] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to determine age-related degradation of betaA3/A1-crystallin in human lenses. The betaA3/A1-crystallin fragments were identified by Western blot analysis using two site-specific anti-betaA3/A1-crystallin antibodies. The first antibody was raised against a N-terminal region (residues 35-66), and the second to the C-terminal (residues 203-214) region of the crystallin. During the analyses, either preparative SDS-PAGE-separated fragments from betaH-crystallin fraction or water-soluble (WS) protein fractions from lenses of different aged donors were used. In lenses from 27- to 30-year-old donors, four major crystallin fragments of about 5, 16, 17, and 18 kDa immunoreacted with the anti-betaA3/A1-N-terminal antibody, suggesting their intact N-terminus but cleaved C-terminus. A similar analysis with the anti-betaA3/A1-C-terminal antibody identified 15-, 18-, 19-, and 20-kDa species and also five species between 4 and 11 kDa that had intact C-terminus but cleaved N-terminus. In lenses from a 5-year-old donor only two crystallin species, a major 15-kDa and a minor 18-kDa species, showed an intact N-terminus and cleaved C-terminus, whereas, eight species with Mr's between 4 and 19 kDa exhibited intact C-terminus but cleaved N-terminus. Upon two-dimensional gel electrophoresis of a betaH-crystallin fraction from the lenses of a 70-year-old donor, a degradation profile almost similar to the crystallin mentioned above was observed. However, the existence of multiple spots with identical Mr's of truncated betaA3/A1-crystallin species on the 2D-gel suggests their existence as isoforms (identical size species with different charges) because of post-translational modifications. Five species of 4, 6, 11, 15, and 18 kDa showed an identical partial N-terminal sequence of N-F-Q-G, suggesting cleavage at the E39-N40 bond during their production. Together, the data suggest that the majority of age-related cleavages in betaA3/A1-crystallin occur at the N-terminal region, with a major cleavage site at the E39-N40 bond generating some of these fragments.
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Affiliation(s)
- O P Srivastava
- School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, 35294, USA.
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8
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Le Breton ER, Carver JA. Solution conformation of bovine lens alpha- and betaB2-crystallin terminal extensions. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1996; 47:9-19. [PMID: 8907494 DOI: 10.1111/j.1399-3011.1996.tb00804.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
alpha- and betaB2-Crystallin are the major proteins in the mammalian lens. Each of these crystallins has short, flexible terminal extensions from its domain core; the two alpha-crystallin subunits have C-terminal extensions of eight and ten amino acids whilst betaB2-crystallin has N- and C-terminal extensions of 15 and 11 amino acids, respectively. The solution conformations of these chemically synthesised extensions have been examined by two-dimensional 1H NMR spectroscopy. The N-terminal extension of betaB2-crystallin and the C-terminal extensions of alpha-crystallin adopt little ordered structure. In the membrane-mimicking solvent trifluoroethanol, the alpha-crystallin extensions are also unstructured. In contrast, the C-terminal extension of betaB2-crystallin in water has a structural preference towards turn-like structures, creating a hydrophobic region involving G198, F200 and P202. In the lens, the C-terminal extension of betaB2-crystallin is the only one of these extensions that interacts to any large extent with other crystallins. The structural preference of the C-terminal extension of betaB2-crystallin may therefore have implications for the role of this extension in crystallin-crystallin interactions.
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Affiliation(s)
- E R Le Breton
- Australian Cataract Research Foundation, Department of Chemistry, The University of Wollongong, New South Wales, Australia
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9
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Kilby GW, Carver JA, Zhu JL, Sheil MM, Truscott RJ. Loss of the C-terminal serine residue from bovine beta B2-crystallin. Exp Eye Res 1995; 60:465-9. [PMID: 7615012 DOI: 10.1016/s0014-4835(05)80061-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Electrospray mass spectrometric (ES-MS) examination of bovine beta-crystallins showed a significant component corresponding in mass to beta B2-crystallin less one serine residue. Tryptic digestion, followed by isolation and characterisation of the C-terminal peptide, demonstrated that this new species has arisen by the loss of the C-terminal serine residue. This phenomenon appears to be age-related since no truncation was detected in beta B2-crystallin from foetal lenses and the proportion of the truncated form, as judged by ES-MS, was lower in beta-crystallin isolated from calf lenses than that from the lenses of 3-year-old animals. This process therefore is similar to a recently reported loss of the C-terminal serine from alpha A-crystallin, which we have confirmed using ES-MS. Loss of a C-terminal serine from both crystallins may indicate the presence of carboxypeptidase-A-like activity in bovine lenses. ES-MS data provided no evidence for a significant degree of phosphorylation of beta B2-crystallin.
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Affiliation(s)
- G W Kilby
- Australian Cataract Research Foundation, University of Wollongong, NSW
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10
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Pennington J, Harding JJ. Identification of the site of glycation of gamma-II-crystallin by (14C)-fructose. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1226:163-7. [PMID: 8204663 DOI: 10.1016/0925-4439(94)90024-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cataract formation in diabetes may be via non-enzymic glycosylation (glycation) of lens proteins due to increased concentrations of sugars present in the lenses of diabetic patients. The objective of this project was to identify the site(s) of glycation of bovine gamma-II-crystallin by [14C]fructose. gamma-II-crystallin was isolated from soluble lens nucleus proteins by gel chromatography, followed by ion-exchange chromatography and was then glycated by incubation with [14C]fructose. Radioactively labelled gamma-II-crystallin was cleaved with trypsin. Affinity chromatography of the tryptic peptides gave a single main peak containing the majority of the radioactivity. This indicated that fructose had reacted at a single site on the protein. Amino acid analysis of this peptide showed it to contain only lysine and a trace amount of glycine. By relating the results of the amino acid analysis to the amino acid sequence of gamma-II-crystallin, it was concluded that the labelled peptide corresponded to the N-terminal dipeptide. The site of glycation of bovine gamma-II-crystallin by fructose was thereby identified as the alpha-NH2 group of the N-terminal glycine.
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Affiliation(s)
- J Pennington
- Nuffield Laboratory of Ophthalmology, University of Oxford, UK
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11
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Nalini V, Bax B, Driessen H, Moss DS, Lindley PF, Slingsby C. Close packing of an oligomeric eye lens beta-crystallin induces loss of symmetry and ordering of sequence extensions. J Mol Biol 1994; 236:1250-8. [PMID: 8120900 DOI: 10.1016/0022-2836(94)90025-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
beta-Crystallins are oligomeric eye lens proteins that are related to monomeric gamma-crystallins. The main sequence difference between the two families is the presence of sequence extensions in the beta-crystallins. A major question concerns the role that these extensions play in mediating interactions at the high protein concentrations found in the lens. The predominant beta-crystallin polypeptide, beta B2, can be crystallized in two different space groups, I222 and C222. The I222 crystal structure revealed that the protein packed as a tetramer with perfect 222 symmetry but that the extensions were disordered. The X-ray structure of the C222 lattice of beta B2 has now been refined at 3.3 A, the structure analysed and compared with the I222 lattice. The protein is also a tetramer with 222 symmetry in the C222 lattice but differs in that parts of the N-terminal extensions have been visualized. In the asymmetric unit of the C222 lattice there are four subunits, each comprising a single polypeptide chain, in which certain flexible loops in the N-terminal domains and the N-terminal extensions have various conformations. The tetramers in the C222 lattice are more tightly packed than in the I222 form. Analysis of the tetramer contacts shows that the sites of interaction break the 222 symmetry of the tetramers. The N-terminal extensions play a major role in directing interactions between tetramers. One of the N-terminal extensions interacts with a hydrophobic patch on the N-terminal domain of another tetramer. These crystallographic observations obtained over a physiological concentration range indicate how, in beta-crystallin oligomers, the N-terminal extensions of beta B2 can switch from interacting with water to interacting with protein depending on their relative concentrations. This could be useful in maintaining a gradient of refractive index.
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Affiliation(s)
- V Nalini
- Laboratory of Molecular Biology, Birkbeck College, London University, UK
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12
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David LL, Shearer TR. Beta-crystallins insolubilized by calpain II in vitro contain cleavage sites similar to beta-crystallins insolubilized during cataract. FEBS Lett 1993; 324:265-70. [PMID: 8405363 DOI: 10.1016/0014-5793(93)80131-d] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Incubation of soluble proteins from rat lens with the protease calpain II caused the precipitation of beta-crystallin polypeptides. Two-dimensional electrophoresis and sequence analysis identified beta-crystallin polypeptides both before and after their precipitation by calpain II. beta-crystallin polypeptides precipitated by calpain were cleaved at their NH2-terminal extensions. These cleavage sites were similar to cleavage sites occurring in beta-crystallin polypeptides precipitated during formation of experimental cataract induced by an overdose of selenite. These data suggested that calpain II caused beta-crystallin insolubilization during cataract formation, and indicated that the process can be mimicked in vitro.
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Affiliation(s)
- L L David
- Department of Oral Molecular Biology, Oregon Health Sciences University, Portland 97201
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13
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Lamba OP, Borchman D, Sinha SK, Shah J, Renugopalakrishnan V, Yappert MC. Estimation of the secondary structure and conformation of bovine lens crystallins by infrared spectroscopy: quantitative analysis and resolution by Fourier self-deconvolution and curve fit. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1163:113-23. [PMID: 8490044 DOI: 10.1016/0167-4838(93)90172-n] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The secondary structure of six bovine lens protein fractions (two alpha, three beta and one gamma-crystallin) are examined in solution and in solid forms for the first time using FTIR spectroscopy. Films of the nuclear and cortical regions of the bovine lens are also examined. The structure is quantitatively estimated from the vibrational analysis of the resolution-enhanced amide-I profile achieved by Fourier self-deconvolution and linear least-squares curve-fit algorithm. All the protein fractions fold predominantly in a beta-pleated sheet structure with little or no alpha-helical domains in solution or in lyophilized solid form. These proteins also retain their predominant beta-sheet conformation in the cellular phospholipid environment of the lens, in conformity with the structure obtained for all the mammalian species examined to date. Despite structural homology, vibrational data indicate subtle structural differences within each class of the crystallins probably due to presence of several minor substructures/subconformations. Substantial high amounts of turns (approx. 40%) observed in the beta-fractions may have a fundamental implication in stabilizing the tertiary structure of the uniquely folded-proteins vital for the transparency of the lens. These proteins in solid KBr-matrix undergo a major structural change, induced primarily by ionic interactions which refold them in a helical conformation. IR spectroscopy together with band-narrowing procedures has proven to be an effective tool to obtain structural information of proteins in solution, as solid substrates or in a complex biological tissue, such as ocular lens.
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Affiliation(s)
- O P Lamba
- Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Kentucky Lions Eye Research Institute 40292
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14
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Carver JA, Cooper PG, Truscott RJ. 1H-NMR spectroscopy of beta B2-crystallin from bovine eye lens. Conformation of the N- and C-terminal extensions. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 213:313-20. [PMID: 8477703 DOI: 10.1111/j.1432-1033.1993.tb17764.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
1H-NMR spectroscopic studies of a 46-kDa homodimer, beta B2-crystallin, from bovine eye lens are presented. beta B2-crystallin has terminal extensions extending from globular N- and C-terminal domains that are well resolved in the NMR spectra, whereas, in the main, resonances from the bulk of the protein are not observed. Using two-dimensional NMR methods on beta B2-crystallin, its synthesised terminal extensions and a proteolysed sample of beta B2-crystallin with a portion of its C-terminus removed, it was possible to assign resonances to most of the amino acids in the terminal extensions. One-dimensional experiments at various pH values provided H-2 chemical shifts for the three terminal extension histidines from which their pKa values were measured. It is concluded that the terminal extensions appear to be of little ordered conformation, are accessible to solvent and flex freely from the main body of the protein. The results of the NMR spectroscopic studies of beta B2-crystallin are in excellent agreement with those for the X-ray crystal structure [Bax, B., Lapatto, R., Nalini, V., Driessen, H., Lindley, P. F., Mahadevan, D., Blundell, T. L. & Slingsby, C. (1990) Nature 347, 776-780]. No change in the spectrum of beta B2-crystallin was observed in the presence of calcium, suggesting that the termini are not involved in calcium binding.
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Affiliation(s)
- J A Carver
- Australian Cataract Research Foundation, Department of Chemistry, University of Wollongong
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15
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Sharma Y, Krishna AG, Balasubramanian D. Alteration of dynamic quaternary structure and calcium-binding ability of beta-crystallin by light. Photochem Photobiol 1993; 57:739-43. [PMID: 8506401 DOI: 10.1111/j.1751-1097.1993.tb02947.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
beta-crystallin, one of the three main constituent proteins of the eye lens, exists as an equilibrium population of oligomeric (beta H), trimeric (beta L1) and dimeric (beta L2) species. This equilibrium is dependent on various factors such as the protein concentration, ionic strength and pH of the medium. We have studied the effect of ultraviolet B radiation on the aggregational patterns of beta-crystallin, using size-exclusion chromatography. Irradiation of a solution of beta H-crystallin at 295 nm for about 30 min causes the deaggregation of the hexameric population into dimers. Irradiation for a longer time, however, produces cross-linked high molecular weight products. Irradiation of a beta L2 solution for 30 min does not perturb the elution profile, while irradiation for a longer time increases the content of beta L1 (trimeric) crystallin. Irradiation also causes a decrease in the calcium-binding affinity of the beta-crystallins.
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Affiliation(s)
- Y Sharma
- Centre for Cellular and Molecular Biology, Hyderabad, India
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16
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Cooper PG, Carver JA, Truscott RJ. 1H-NMR spectroscopy of bovine lens beta-crystallin. The role of the beta B2-crystallin C-terminal extension in aggregation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 213:321-8. [PMID: 8477704 DOI: 10.1111/j.1432-1033.1993.tb17765.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
1H-NMR spectroscopic studies of bovine eye lens beta-crystallin aggregates (dimer, trimer and octomer) are presented. The NMR spectra for all three beta-crystallin aggregates are dominated by resonances from the beta B2 subunit, particularly from the N- and C-terminal extensions of this subunit. Resonances from other beta subunits, which all have terminal extensions, are, in general, absent from spectra of the beta-crystallin aggregates. Therefore, the beta B2 subunit and, in particular its terminal extensions, has enhanced flexibility compared to the other beta-crystallin subunits. Furthermore, resonances arising from the C-terminal extension of beta B2-crystallin are not present in the spectrum of the octomer, which is consistent with the C-terminal extension binding in this aggregate and hence being involved in large aggregate formation. A possible interaction between the C-terminal extension of beta B2 and the hydrophobic beta B1 subunit, which is only found in the octomer, is discussed. At higher temperatures (45 degrees C) in the octomer, partial exposure of the C-terminal extension of beta B2 occurs indicating that the octomer may be starting to break up into smaller aggregates.
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Affiliation(s)
- P G Cooper
- Australian Cataract Research Foundation, Department of Chemistry, University of Wollongong
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17
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Zarina S, Abbasi A, Zaidi ZH. Primary structure of beta s-crystallin from human lens. Biochem J 1992; 287 ( Pt 2):375-81. [PMID: 1445197 PMCID: PMC1133175 DOI: 10.1042/bj2870375] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The complete primary structure of beta s-crystallin from human lens is reported. The sequence was elucidated by automatic Edman degradation of tryptic and CNBr peptides. The blocked N-terminal dipeptide was identified by fast-atom-bombardment mass spectroscopy. The sequence comparison with other members of crystallin family reveals a closer relationship to human gamma-crystallin (53% identity) than with beta A3/A1 crystallin (37% identity). The structure, evolutionary characteristics and role of beta s-crystallin in lens are discussed.
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Affiliation(s)
- S Zarina
- H.E.J. Research Institute of Chemistry, University of Karachi, Pakistan
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18
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Datiles MB, Schumer DJ, Zigler JS, Russell P, Anderson L, Garland D. Two-dimensional gel electrophoretic analysis of human lens proteins. Curr Eye Res 1992; 11:669-77. [PMID: 1521468 DOI: 10.3109/02713689209000740] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Human lens proteins from clear lenses were separated and identified using two-dimensional polyacrylamide electrophoresis. Isoelectric focusing, both equilibrium and non-equilibrium, was performed in the first dimension and SDS electrophoresis in the second dimension. Proteins were identified by Western blotting and sequencing techniques and by comparison with patterns obtained with purified crystallin fractions. Analyses were performed on total urea soluble proteins of lenses varying in age from fetal to 73 yr. Several hundred protein spots representing crystallins, cytoskeletal proteins and enzymes were resolved in the fetal lens. In the older lenses there was a dramatic increase in the number of protein species in the molecular weight range of the crystallins and a reduced number of discrete protein species visible at molecular weights greater than 50,000. Conversely, a number of proteins below approximately 15 kDa were visible even in the fetal lens. The number and amount of polypeptides in this molecular weight range were increased in the older lenses. Many of these low molecular weight species could be assigned to either the alpha-, beta- or gamma-crystallin fractions. An age dependent increase in the number of acidic species of both crystallins and other proteins, such as, glyceraldehyde 3-phosphate dehydrogenase was observed as well as the loss or mobility change of gamma-crystallin. Two-dimensional gel electrophoresis provides a sensitive and practical technique for characterizing all of the proteins of the human lens.
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Affiliation(s)
- M B Datiles
- National Eye Institute, National Institutes of Health, Bethesda, MD
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19
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Abstract
Bovine lens beta H-crystallin, isolated at pH 6.7, undergoes reversible dissociation into dimers and an intermediate size of oligomer (peak A) at pH 5.4. Peak A is enriched in the beta B1 subunit but lacks beta B2, whereas beta B2 is a major component of the dimers. A method for isolation of beta B1 from peak A is described. The pH dependence of the dissociation-reassociation suggests that histidines on the surface of the dimers become buried in the assembly of beta H-crystallin. The positions of the four histidines on the surface of the compact domains of each subunit of the beta B2 homodimer are shown. The beta B1-enriched oligomer has a much lower solubility compared with the beta B2 containing beta H-crystallin. It is possible that beta B2 plays a role in solubilizing beta-crystallin aggregates.
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Affiliation(s)
- O A Bateman
- Department of Crystallography, Birkbeck College, London, U.K
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20
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Abstract
Recent advances in understanding the mechanism of selenite cataract have resulted from locating the cleavage sites on proteolyzed beta-crystallins from the cataract, mimicking the insolubilization of crystallins found in the cataract in an in vitro system, studying cataract produced in lenses cultured in selenite, and permanently or temporarily reducing the rate formation of selenite cataract by use of various inhibitors. The present review discusses the selenite cataract as a useful model for understanding the role calcium-induced proteolysis in cataract formation.
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Affiliation(s)
- T R Shearer
- Department of Oral Biochemistry, School of Dentistry, Oregon Health Sciences University, Portland 97201
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21
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Tardieu A, Vérétout F, Krop B, Slingsby C. Protein interactions in the calf eye lens: interactions between beta-crystallins are repulsive whereas in gamma-crystallins they are attractive. EUROPEAN BIOPHYSICS JOURNAL : EBJ 1992; 21:1-12. [PMID: 1516556 DOI: 10.1007/bf00195438] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Non-specific interactions in beta- and gamma-crystallins have been studied by solution X-ray scattering and osmotic pressure experiments. Measurements were carried out as a function of protein concentration at two ionic strengths. The effect of temperature was tested between 7 degrees C and 31 degrees C. Two types of interactions were observed. With beta-crystallin solutions, a repulsive coulombic interaction could be inferred from the decrease of the normalized X-ray scattering intensity near the origin with increasing protein concentration and from the fact that the osmotic pressure increases much more rapidly than in the ideal case. As was previously observed with alpha-crystallins, such behaviour is dependent upon ionic strength but is hardly affected by temperature. In contrast, with gamma-crystallin solutions, the normalized X-ray scattering intensity near the origin increases with increasing protein concentration and the osmotic pressure increases less rapidly than in the ideal case. Such behaviour indicates that attractive forces are predominant, although we do not yet know their molecular origin. Under our experimental conditions, the effect of temperature was striking whereas no obvious contribution of the ionic strength could be seen, perhaps owing to masking by the large temperature effect. The relevance of the different types of non-specific interactions for lens function is discussed.
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Affiliation(s)
- A Tardieu
- Centre de Génétique Moléculaire, CNRS, Gif sur Yvette, France
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22
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van Rens GL, de Jong WW, Bloemendal H. A superfamily in the mammalian eye lens: the beta/gamma-crystallins. Mol Biol Rep 1992; 16:1-10. [PMID: 1545779 DOI: 10.1007/bf00788747] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- G L van Rens
- Dept. of Biochemistry, Univ. of Nijmegen, The Netherlands
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23
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Lapatto R, Nalini V, Bax B, Driessen H, Lindley PF, Blundell TL, Slingsby C. High resolution structure of an oligomeric eye lens beta-crystallin. Loops, arches, linkers and interfaces in beta B2 dimer compared to a monomeric gamma-crystallin. J Mol Biol 1991; 222:1067-83. [PMID: 1762146 DOI: 10.1016/0022-2836(91)90594-v] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
beta-Crystallins are polydisperse, oligomeric structural proteins that have a major role in forming the high refractive index of the eye lens. Using single crystal X-ray crystallography with molecular replacement, the structure of beta B2 dimer has been solved at 2.1 A resolution. Each subunit comprises an N and C-terminal domain that are very similar and each domain is formed from two similar "Greek key" motifs related by a local dyad. Sequence differences in the internally quadruplicated molecules, analysed in terms of their beta-sheets, hairpins and arches, give rise to structural differences in the motifs. Whereas the related family of gamma-crystallins are monomers, beta-crystallins are always oligomers. In the beta B2 subunit, the domains, each comprising two motifs, are separated by an extended linking peptide. A crystallographic 2-fold axis relates the two subunits of the dimer so that the N-terminal domain of one subunit of beta B2 and the C-terminal domain of the symmetry-related subunit are topologically equivalent to the two covalently connected domains of gamma B-crystallin. The intersubunit domain interface is very similar to the intradomain interface of gamma B, although many sequence differences have resulted in an increase in polar interactions between domains in beta B2. Comparison of the structures of beta B2 and gamma B-crystallins shows that the two families differ largely in the conformation of their connecting peptides. A further extensive lattice contact indicates a tetramer with 222 symmetry. The ways in which insertions and extensions in the beta-crystallin effect oligomer interactions are described. The two kinds of crystallin are analysed for structural features that account for their different stabilities. These studies are a basis for understanding formation of higher aggregates in the lens.
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Affiliation(s)
- R Lapatto
- Laboratory of Molecular Biology, Birkbeck College, London University, U.K
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24
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van Rens GL, Hol FA, de Jong WW, Bloemendal H. Presence of hybridizing DNA sequences homologous to bovine acidic and basic beta-crystallins in all classes of vertebrates. J Mol Evol 1991; 33:457-63. [PMID: 1960742 DOI: 10.1007/bf02103138] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The eye lens beta-crystallins in cow and chicken are encoded by a family of at least six genes. In order to assess the distribution of the corresponding genes among other vertebrates we hybridized beta-crystallin sequences (beta A2, beta A3/A1, beta A4, beta B1, beta B2, beta B3), isolated from a bovine lens cDNA library, to Southern blots on which EcoR1-digested chromosomal DNA was blotted from different vertebrate species. These included human, chimpanzee, calf, rat, pigeon, duck, monitor lizard, toad, trout, and lamprey. Positive hybridization signals were found in the representatives of virtually all classes of vertebrates. The basic beta B-crystallins gave hybridization signals in more species than the acidic beta A ones. In monitor lizard and toad the weakest hybridization signals for basic crystallin probes were found. For acidic crystallin probes the distribution pattern was more simple; among cold-blooded vertebrates a signal for beta A2 was found in trout and lamprey, for beta A4 in trout, and for beta A3/A1 only in toad. The results demonstrate that the duplications leading to the beta-crystallin gene family occurred before or during the earliest stages of vertebrate evolution.
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Affiliation(s)
- G L van Rens
- Department of Biochemistry, University of Nijmegen, The Netherlands
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25
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Chirgadze YU, Nevskaya N, Vernoslova E, Nikonov S, Sergeev YU, Brazhnikov E, Fomenkova N, Lunin V, Urzhumtsev A. Crystal structure of calf eye lens gamma-crystallin IIIb at 2.5 A resolution: its relation to function. Exp Eye Res 1991; 53:295-304. [PMID: 1936165 DOI: 10.1016/0014-4835(91)90233-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The crystal structure of gamma-crystallin IIIb (gamma C) from calf eye lens has been refined at 2.5 A resolution. The molecule of about 21 kDa consists of two similar domains. Each domain is composed of two motifs with the 'Greek key' topology which form a pair of four-stranded beta-sheets with an antiparallel packing. The molecule has three hydrophobic cores: one within each domain and one between them. Six of the eight functionally important cysteines are located within the N-domain, and only two in the C-domain. Several large clusters of charged residues are at the surface of the molecule. Surface residues Val 101, Met 103 and Leu 155 are important for packing of molecules in crystal medium and possibly in the lens. Features of the gamma-crystallin IIIb molecule which may be related to its function in the vertebrate eye lens are briefly discussed. An attempt has been made to correlate molecular characteristics with some general properties of the eye lens such as high density and refractive index gradients and strong stability of the lens during an organism's lifetime.
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Affiliation(s)
- Y u Chirgadze
- Institute of Protein Research, Academy of Sciences of the U.S.S.R., Moscow
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26
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van Rens GL, Driessen HP, Nalini V, Slingsby C, de Jong WW, Bloemendal H. Isolation and characterization of cDNAs encoding beta A2- and beta A4-crystallins: heterologous interactions in the predicted beta A4-beta B2 heterodimer. Gene 1991; 102:179-88. [PMID: 1874445 DOI: 10.1016/0378-1119(91)90076-n] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Except for the two acidic chains, beta A2 and beta A4, the primary structures of all bovine beta-crystallins have previously been elucidated, either by direct protein sequencing or prediction from cDNA sequencing. Both beta A2 and beta A4 were found to be synthesized in half-year-old calf lenses and are therefore likely to be present in a cDNA bovine library constructed from mRNA isolated from lenses of that age. A large number of cDNA clones was screened with all available crystallin, actin, vimentin and lens membrane protein MP26 probes and finally with a randomly primed mRNA probe. Clones positive for the latter, but negative for known lens proteins, were isolated and sequenced. beta A2, comprising 197 aa, and beta A4, comprising 209 aa, were identified. Both proteins have a conserved two-domain structure and an N-terminal extension which is variable. A three-dimensional model of the structure of beta A4 was made based on the coordinates of one subunit from the beta B2 dimer which has recently been solved using x-ray diffraction techniques. The resulting heterodimer structure, together with the compiled bovine beta-crystallin sequences, was used to indicate those regions of the sequences which distinguish acidic from basic beta-crystallins with a view to defining structural features necessary for subunit recognition in beta-crystallin aggregates. With the aid of the present data, the complete evolutionary tree of the bovine beta-crystallin family has been constructed, which confirms the early separation of the genes encoding the three acidic and the three basic beta-crystallins.
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Affiliation(s)
- G L van Rens
- Department of Biochemistry, University of Nijmegen, The Netherlands
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27
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Abstract
In soluble extracts of bird lenses, crystallin subunits of apparent sizes between 30kDa and 40kDa show considerable variability in both abundance and mobility in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE). This is only partly due to the taxon-specific distribution of lactate dehydrogenase-B (LDH-B)/epsilon-crystallin. Here we show that, in spite of high conservation in primary sequence, beta B1-crystallin subunits of avian lenses have a markedly slower migration in SDS PAGE than those of mammals and that the apparent subunit size of beta B1-crystallin varies among birds. This may be at least partly due to unusual post-translational modifications, since beta B1-crystallins of adult birds react strongly in a glycan detection procedure. No other crystallins in birds or mammals share this strong reaction. Modification of beta B1-crystallin could have interesting consequences for the formation of high molecular weight beta-crystallin aggregates in bird lenses.
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Affiliation(s)
- G Wistow
- Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892
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28
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29
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Abstract
Different crystallins (alpha, beta H, beta L and LMW) were isolated from bovine lenses. Lyophilized samples of single components (homoaggregates) and those of mixtures (heteroaggregates) were exposed to HCI vapor in a high vacuum vapor sorption apparatus. Lyophilized 5-microns sections of bovine lens were similarly exposed to HCI vapors. Sorption and desorption isotherms were obtained at two temperatures on all samples. Fourier transform infrared (FT IR) spectroscopy was conducted on solid samples of crystallin with and without irreversibly sorbed HCI gas. From the IR spectra the nature of interaction between HCI and protein were ascertained. From the sorption parameters, mainly from the irreversibly sorbed HCI, the accessibilities of homo and hetero aggregates were calculated. The accessibilities provided information on the preferential interactions among crystallins. One of the main conclusions derived from this and also from previous ammonia sorption studies is that the supramolecular organization in the lens fibers is not governed solely by the thermodynamically preferential interactions of crystallins, but also by other possibly cytoskeletal organizations of crystallins.
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Affiliation(s)
- F A Bettelheim
- Chemistry Department, Adelphi University, Garden City, NY 11530
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30
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Bax B, Lapatto R, Nalini V, Driessen H, Lindley PF, Mahadevan D, Blundell TL, Slingsby C. X-ray analysis of beta B2-crystallin and evolution of oligomeric lens proteins. Nature 1990; 347:776-80. [PMID: 2234050 DOI: 10.1038/347776a0] [Citation(s) in RCA: 228] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The beta, gamma-crystallins form a class of homologous proteins in the eye lens. Each gamma-crystallin comprises four topologically equivalent, Greek key motifs; pairs of motifs are organized around a local dyad to give domains and two similar domains are in turn related by a further local dyad. Sequence comparisons and model building predicted that hetero-oligomeric beta-crystallins also had internally quadruplicated subunits, but with extensions at the N and C termini, indicating that beta, gamma-crystallins evolved in two duplication steps from an ancestral protein folded as a Greek key. We report here the X-ray analysis at 2.1 A resolution of beta B2-crystallin homodimer which shows that the connecting peptide is extended and the two domains separated in a way quite unlike gamma-crystallin. Domain interactions analogous to those within monomeric gamma-crystallin are intermolecular and related by a crystallographic dyad in the beta B2-crystallin dimer. This shows how oligomers can evolve by conserving an interface rather than connectivity. A further interaction between dimers suggests a model for more complex aggregates of beta-crystallin in the lens.
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Affiliation(s)
- B Bax
- Department of Crystallography, Birkbeck College, London University, UK
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31
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Leunissen JA, van den Hooven HW, de Jong WW. Extreme differences in charge changes during protein evolution. J Mol Evol 1990; 31:33-9. [PMID: 2116529 DOI: 10.1007/bf02101790] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The maintenance of a proper distribution of charged amino acid residues might be expected to be an important factor in protein evolution. We therefore compared the inferred changes in charge during the evolution of 43 protein families with the changes expected on the basis of random base substitutions. It was found that certain proteins, like the eye lens crystallins and most histones, display an extreme avoidance of changes in charge. Other proteins, like phospholipase A2 and ferredoxin, apparently have sustained more charged replacements than expected, suggesting a positive selection for changes in charge. Depending on function and structure of a protein, charged residues apparently can be important targets for selective forces in protein evolution. It appears that actual biased codon usage tends to decrease the proportion of charged amino acid replacements. The influence of nonrandomness of mutations is more equivocal. Genes that use the mitochondrial instead of the universal code lower the probability that charge changes will occur in the encoded proteins.
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Affiliation(s)
- J A Leunissen
- Department of Biochemistry, University of Nijmegen, The Netherlands
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32
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Russell P, Chambers C. Interaction of an altered beta-crystallin with other proteins in the Philly mouse lens. Exp Eye Res 1990; 50:683-7. [PMID: 2373162 DOI: 10.1016/0014-4835(90)90114-a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
An altered beta B2-crystallin is synthesized in the lens of the Philly mouse. This beta B2 has a more acidic isoelectric point than the beta B2 that is isolated from normal mouse lens. The altered beta B2 is immunologically reactive with antibody to the amino terminal of the beta B2-crystallin, but appears to be present in only very small quantities in the Philly lens. When the soluble proteins are isolated from the Philly lens and chromatographed by gel exclusion chromatography, the beta B2 can be found primarily in the heavy molecular weight fraction. Some immunoreactive material was also found throughout the higher molecular weight beta-crystallin region, beta H, and the lower molecular weight region, beta L. These results would indicate that the altered beta B2-crystallin in the Philly lens can interact with the other beta-crystallins in the lens; however, interactions of the beta B2-crystallin with the other proteins of the lens may cause rapid aggregation of the cellular proteins leading to the formation of the heavy molecular weight material. The increased number of these aggregates may eventually lead to the cataract formation in the Philly mouse.
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Affiliation(s)
- P Russell
- National Institutes of Health, Bethesda, MD 20892
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33
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Abstract
The water binding properties of bovine lens crystallins, alpha, beta H, beta L and low molecular weight (LMW), were investigated with different techniques. The water sorptive capacity was obtained in high vacuum sorption experiments volumetrically, and also gravimetrically in controlled atmosphere experiments. The two methods gave reproducible isotherms. The strongly sorbed water (bound water) was evaluated from the B.E.T. monolayer and from the values of isosteric heats. The bound water content of the crystallins were also measured by combined differential scanning calorimetry and thermogravimetric analysis. The non-freezable water contents calculated as % of the total water content and also as g g-1 crystallin, were used as an indicator for bound water. In all three different techniques, the following order was obtained: beta H greater than alpha greater than beta L = LMW.
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Affiliation(s)
- F A Bettelheim
- Chemistry Department, Adelphi University, Garden City, NY 11530
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34
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Sharma Y, Rao CM, Rao SC, Krishna AG, Somasundaram T, Balasubramanian D. Binding Site Conformation Dictates the Color of the Dye Stains-All. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)30024-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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35
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Andley UP, Clark BA. Photoreactions of human lens monomeric crystallins. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 997:284-91. [PMID: 2548626 DOI: 10.1016/0167-4838(89)90199-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Human lens beta s- and gamma A-crystallins exhibit very similar tryptophan fluorescence emission maxima (329 nm). gamma A isolated from infant human lenses is photo-oxidized by 300 nm irradiation and forms water-insoluble aggregates; beta s or gamma A from young human lenses form a small amount of water-soluble crosslinked species. At least part of the mechanism of photodamage by 300 nm irradiation is photogeneration of the oxidant H2O2 via the generation of O2- radical, this reaction occurs via photosensitization by the tryptophan photo-oxidation product N-formylkynurenine (N-FK) or related species. These results indicate that even though the tryptophan residues of beta s- and gamma A-crystallins are in hydrophobic (buried) microenvironments as compared to those of the alpha- and beta-crystallins, the photogeneration of N-FK is sufficient to produce O2- and H2O2.
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Affiliation(s)
- U P Andley
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston 02114
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36
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Abstract
A new crystal form of the bovine oligomeric lens protein beta B2 has been grown in the presence of calcium acetate. The crystals are orthorhombic, I222 or I2(1)2(1)2(1), with cell dimensions a = 77.8 A, b = 83.6 A, c = 109.2 A. This new crystal form, which diffracts to at least 2.5 A, has a and b cell dimensions that are half those of the original crystal form, although there is no simple relationship between the c cell dimensions. The new crystal form reported here contains only one subunit per asymmetric unit, indicating that the dimer lies on a crystallographic 2-fold axis, and is a suitable candidate for molecular replacement studies.
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Affiliation(s)
- B Bax
- Laboratory of Molecular Biology, Department of Crystallography, Birkbeck College, University of London, U.K
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37
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Andley UP, Clark BA. The effects of near-UV radiation on human lens beta-crystallins: protein structural changes and the production of O2- and H2O2. Photochem Photobiol 1989; 50:97-105. [PMID: 2762385 DOI: 10.1111/j.1751-1097.1989.tb04134.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
beta-Crystallins (beta 1-, beta 2- and beta 3-crystallin) comprise nearly half the protein of the human lens. The effect of near-UV radiation, which is one of the possible risk factors in cataract formation, on the beta-crystallins is investigated in this study. Protein intersubunit crosslinking, change in charge of the protein subunits to more acidic species and changes in protein tertiary structure (conformation) by 300 nm irradiation are reported. The fluorescence yield of protein tryptophan residues decreases by 300 nm irradiation. There is an increase in nontryptophan fluorescence (lambda cx 340 nm, lambda cm 400-600 nm), and in protein absorption at 340 nm, due to the formation of tryptophan photooxidation products. Both tryptophan and its oxidation products can be photoexcited by 300 nm irradiation and the latter are known to be good photosensitizers. The results provide evidence for the generation of H2O2 in the irradiated human beta-crystallin solutions by the Type I photosensitizing action of the chromophores absorbing at 300 nm. The H2O2 is generated via the intermediate production of O2 anion; the latter spontaneously dismutates to H2O2, presumably via O2- protein interactions. The amount of H2O2 generated per absorbed photon is compared for various solutions of beta 1-, beta 2- and beta 3-crystallins from human lenses of different age.
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38
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van Rens GL, Raats JM, Driessen HP, Oldenburg M, Wijnen JT, Khan PM, de Jong WW, Bloemendal H. Structure of the bovine eye lens gamma s-crystallin gene (formerly beta s). Gene 1989; 78:225-33. [PMID: 2476364 DOI: 10.1016/0378-1119(89)90225-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The organization of a number of crystallin genes has already been resolved. One of the remaining genes of which the structure was hitherto unknown is the gamma s gene (formerly beta s). We determined the complete sequence of the bovine gamma s-crystallin-coding gene, apart from the middle region of the first intron. Since it contains three exons and two introns, we conclude that the former beta s, also at the gene level is gamma-crystallin-like. However, it is located on chromosome 3, in contrast to other gamma genes which occur in tandem on the human chromosome 2.
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Affiliation(s)
- G L van Rens
- Department of Biochemistry, University of Nijmegen, The Netherlands
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Voorter CE, Bloemendal H, de Jong WW. In vitro and in vivo phosphorylation of chicken beta B3-crystallin. Curr Eye Res 1989; 8:459-65. [PMID: 2544346 DOI: 10.3109/02713688909000026] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Incubations of chicken lens homogenates with [32P]-ATP revealed the phosphorylation of a 28 kDa protein, and phosphoamino acid analysis of the phosphorylated protein showed the presence of phosphoserine. The protein is present in the beta-crystallin fraction and after purification and partial sequence determination, by way of peptide mapping and subsequent amino acid analyses and Edman degradation, this 28 kDa protein was identified as the beta B3-crystallin subunit, based on its homology with the bovine and rat orthologue. From phosphate content determination it could be concluded that this chicken beta B3 subunit contains in vivo 2 mol phosphate/mol polypeptide.
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Affiliation(s)
- C E Voorter
- Department of Biochemistry, University of Nijmegen, The Netherlands
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Hendriks W, Mulders JW, Bibby MA, Slingsby C, Bloemendal H, de Jong WW. Duck lens epsilon-crystallin and lactate dehydrogenase B4 are identical: a single-copy gene product with two distinct functions. Proc Natl Acad Sci U S A 1988; 85:7114-8. [PMID: 3174623 PMCID: PMC282134 DOI: 10.1073/pnas.85.19.7114] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
To investigate whether or not duck lens epsilon-crystallin and duck heart lactate dehydrogenase (LDH) B4 are the product of the same gene, we have isolated and sequenced cDNA clones of duck epsilon-crystallin. By using these clones we demonstrate that there is a single-copy Ldh-B gene in duck and in chicken. In the duck lens this gene is overexpressed, and its product is subject to posttranslational modification. Reconstruction of the evolutionary history of the LDH protein family reveals that the mammalian Ldh-C gene most probably originated from an ancestral Ldh-A gene and that the amino acid replacement rate in LDH-C is approximately 4 times the rate in LDH-A. Molecular modeling of LDH-B sequences shows that the increased thermostability of the avian tetramer might be explained by mutations that increase the number of ion pairs. Furthermore, the replacement of bulky side chains by glycines on the corners of the duck protein suggests an adaptation to facilitate close packing in the lens.
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Affiliation(s)
- W Hendriks
- Department of Biochemistry, University of Nijmegen, The Netherlands
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