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VR Harrington, OP Srivastava; Age-Related Degradation of -Crystallin in Human Lenses . Invest. Ophthalmol. Vis. Sci. 2002;43(13):474.
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Purpose: The aims of this study were to identify α-crystallin fragments in water-soluble (WS) protein-fractions of aging normal human lenses and to determine in vivo cleavage sites in parent αA- and αB-crystallins. Methods: The individual crystallin fractions (HMW proteins, α-, ß-, and γ-crystallins) from WS protein fractions of aging normal human lenses were separated by size-exclusion column chromatography. The α-crystallin fractions (identified by SDS-PAGE) were subjected to two-dimensional (2D) gel electrophoresis. The desired fragments (Mr < 20 kDa) were digested by trysin and analyzed by mass spectrometry. Results: On a 2D-gel, eight species (Mr < 20 kDa) were seen in the α-crystallin fractions of lenses from a 13-year-old donor. In contrast, forty species were observed in a similar analysis in the α-crystallin fractions of lenses from 21 to 26-year-old donors. Mass spectrometric analysis revealed that in the lenses of the 13-year-old donor, a 15.8 kDa species (αA) was N-terminally cleaved, two species with Mr 16.2 kDa (αA) and 18.4 kDa (αB) were C-terminally cleaved, and four species with Mr 15 kDa (αA), 15.8 kDa (αA), and two species with Mr 18.4 kDa (αB) were N- and C- terminally cleaved. Conclusion: Both αA-and αB-crystallins show in vivo degradation in young human lenses of a 13-year-old donor. This in vivo degradation increases with aging.
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