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P. Santhoshkumar, P. Udupa, E. Cheney, K. Sharma; Effect of Interaction of Low Molecular Weight Crystallin Fragments With Intact Crystallins . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2009.
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There is an increase in crystallin fragment concentration in aged and cataract human lens. The cleaved fragments are known to interact with intact lens crystallins. The current study was undertaken to identify the crystallin fragments from aged human lens and study the effect of their interactions with intact lens crystallins.
Crystallin fragments were isolated from the water insoluble fraction of aged and cataract human lenses using 6M urea and filtering through a 10kDa filter. The filtrate was desalted and analyzed by Mass spectrometry to identify and sequence the peptides. Three crystallin fragments, αB(1–18), ßA3/A1(59–74) and γS(167–178) found in all analyzed lenses were chemically synthesized. The interaction of the peptides with intact α, ß and γ–crystallins was studied using size–exclusion chromatography, dynamic light scattering, HPLC, and by performing chaperone assays.
Peptides derived from αB–crystallin and ßA3/A1 caused a concentration dependent increase in the light scattering of ßL, and γ–crystallins during thermal aggregation assay while γS peptide had no effect. Addition of αB and ßA3/A1 peptide to a fraction of ßL–crystallin that aggregates on prolonged incubation at 37oC enhances the aggregation by 8 and 10–folds respectively. Interaction with ßA3/A1 peptide caused a 5–fold increase in molar mass and a significant increase in polydispersity of αB–crystallin whereas the interaction of αB– with αB peptide resulted in nearly 2–fold increase in molar mass. Additionally, the peptides also decreased the ability of α–crystallin to function as a molecular chaperone. Replacing the hydrophobic residues in peptides decreased their ability to enhance crystallin aggregation.
αB(1–18) and ßA3/A1(59–74) fragments present in human lenses interact with intact crystallins and induce protein aggregation. Therefore it seems that in vivo generation and interaction of crystallin fragments with crystallins is one of the key events in lens ageing and cataractogenesis.
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