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SQ Huynh, S McCall, OP Srivastav; Cataract-Specific Degradation of Alpha-Crystallin Fragments in Human Lenses . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3558.
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Purpose: The objectives of the study were to determine cataract-specific degradation of alpha-crystallin and the presence of these fragments in the high molecular weight (HMW) protein and alpha-crystallin fractions of human lenses. Methods: The individual crystallins (HMW proteins, alpha-, betaH-, betaL- and gamma-crystallins) were separated from water-soluble protein fractions of cataractous and age-matched normal lenses by size-exclusion chromatography. A comparative two-dimensional gel electrophoresis of crystallin fragments present in alpha-crystallin and HMW-protein fractions was carried out followed by mass spectrometric analysis of desired species. Results: A comparative SDS-PAGE analysis showed that the cataractous HMW protein- and alpha-crystallin fractions contained relatively greater number of crystallin fragments than normal lenses. On a similar comparative two-dimensional gel electrophoretic analysis of HMW proteins, four spots were present only in the cataractous lenses and two spots only in the normal lenses. By a similar comparative analysis of alpha-crystallin fractions, the presense of two spots was identified only in the cataractous lenses and sixteen spots in the normal lenses. Each spot was trypsin digested and used for mass spectrometric analysis. The majority of the spots from both alpha-crystallin- and HMW-protein fractions were fragments of either alpha-A or alpha-B crystallins. Further, several fragments of the alpha-A and alpha-B-crystallins disappeared during cataractogenesis, suggesting their cataract-specific degradation. Conclusion: During human senile cataractogenesis, major changes in the fragments of alpha-A- and alpha-B-crystallins were observed. These changes were cataract-specific and not age-related. The fragments of alpha-A and alpha-B-crystallins showed cataract-specific degradation.
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