The sequence of human betaB1-crystallin cDNA allows mass spectrometric detection of betaB1 protein missing portions of its N-terminal extension.
ABSTRACT The sequence of human betaB1-crystallin cDNA encoded a protein of 251 amino acids in length. Mass spectrometric analysis of intact betaB1 from young human lens confirmed the deduced amino acid sequence. Lenses of human donors newborn to 27 years of age also contained partially degraded forms of betaB1 missing 15, 33, 34, 35, 36, 39, 40, and 41 amino acid residues from their N-terminal extensions. The similarity of the cleavage site between residues 15 and 16 in human betaB1 to the cleavage occurring in bovine betaB1 suggested that lenses of both species may contain a similar proteolytic activity. The remaining cleavage sites occurring in human betaB1 did not closely match those occurring in other species, possibly due to the widely divergent amino acid sequence of the N-terminal extension of betaB1 amoung species. Results from animal models suggest that cleavage of the N-terminal extension of betaB1-crystallin could enhance protein insolubilization and cataract in lens. However, the presence of partially degraded betaB1-crystallins in both water-soluble and water-insoluble fractions of lenses of young donors suggested that the rate that proteolyzed betaB1-crystallins become water-insoluble is relatively slow in humans.
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ABSTRACT: To determine putative alterations in the major lenticular proteins in Wistar rats of different ages and to compare these alterations with those occurring in rats with selenite-induced cataract. Lenticular transparency was determined by morphological examination using slit-lamp biomicroscopy. Alterations in lenticular protein were determined by sodium dodecyl sulfate-PAGE (SDS-PAGE) and confirmed immunologically by western blot. Morphological examination did not reveal observable opacities in the lenses of the rats of different age groups; however, dense nuclear opacities were noted in lenses of rats in the selenite-cataract group. Western blot assays revealed age-related changes in soluble and urea-soluble lenticular proteins. Decreased alphaA- and betaB1-crystallins in the soluble fraction and aggregation of alphaA-crystallin, in addition to the degraded fragment of betaB1-crystallin, in the urea-soluble fraction appeared to occur in relation to increasing age of the rats from which the lenses were taken; similarly, cytoskeletal proteins appeared to decline with increasing age. The lenses from rats in the selenite-cataract group exhibited similar changes, except that there was also high molecular weight aggregation of alphaA-crystallin. The results of this study suggest that there is loss, as well as aggregation, of alphaA-crystallin in the aging rat lens, although there is no accompanying loss of lenticular transparency.Molecular vision 01/2010; 16:445-53. · 1.99 Impact Factor
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ABSTRACT: β-Crystallins are structural proteins maintaining eye lens transparency and opacification. Previous work demonstrated that dimerization of both βA3 and βB2 crystallins (βA3 and βB2) involves endothermic enthalpy of association (∼8 kcal/mol) mediated by hydrophobic interactions. Thermodynamic profiles of the associations of dimeric βA3 and βB1 and tetrameric βB1/βA3 were measured using sedimentation equilibrium. The homo- and heteromolecular associations of βB1 crystallin are dominated by exothermic enthalpy (-13.3 and -24.5 kcal/mol, respectively). Global thermodynamics of βB1 interactions suggest a role in the formation of stable protein complexes in the lens via specific van der Waals contacts, hydrogen bonds and salt bridges whereas those β-crystallins which associate by predominately hydrophobic forces participate in a weaker protein associations.PLoS ONE 01/2012; 7(1):e29227. · 3.73 Impact Factor
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ABSTRACT: The crystallin family of proteins comprise the main structural proteins of the vertebrate lens and have been classified into alpha-, beta-, and gamma- families. Several of the beta-crystallin proteins have been detected in the retina where they are each localized to different compartments of rod and cone photoreceptors. Functionally, beta-crystallins have been implicated in the protection of the retina from intense light exposure. Two members of the beta-crystallins, CRYBB1 and CRYBB2, have been identified in drusen preparations isolated from the retina of donor eyes of patients with age-related macular degeneration (AMD), the leading cause of blindness in the elderly population of developed countries. We therefore investigated CRYBB1 and CRYBB2 as candidate genes for AMD in 274 unrelated patients. A mutation screen of the entire coding region of the CRYBB1gene uncovered eight sequence variations, including three missense changes, two intronic changes and three isocoding changes. A mutation screen of the entire coding region of the CRYBB2 gene uncovered three sequence variations, one isocoding change and two intronic changes. Although variant alleles of the CRYBB1 and CRYBB2 genes were found, none are considered pathogenic.Ophthalmic Genetics 09/2010; 31(3):129-34. · 1.07 Impact Factor