Beta-crystallins insolubilized by calpain II in vitro contain cleavage sites similar to beta-crystallins insolubilized during cataract.
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.
David
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LL
Department of Oral Molecular Biology, Oregon Health Sciences University, Portland 97201.
Shearer
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TR
D000595:Amino Acid Sequence; D000818:Animals; D002154:Calpain / Q000737:chemistry*; D002386:Cataract / Q000503:physiopathology*; D002851:Chromatography, High Pressure Liquid; D003459:Crystallins / Q000737:chemistry*; D015180:Electrophoresis, Gel, Two-Dimensional; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility
D003459:Crystallins; D002154:Calpain