Crystallin proteins in lenses of hereditary cataractous rat, ICR/f.

ICR/f mutation in rat, an inherited disorder, is characterized by the development of cataracts. In this study, we analyzed and compared the crystallins in normal and cataractous rat lenses using gel filtration and two-dimensional gel electrophoresis, and determined the transglutaminase activities and Ca2+ content in the mutant and normal lenses. The Ca2+ content about 10-fold and the activity of transglutaminase was about 1.8-fold higher in the cataractous lenses than in the normal lenses. Analysis of the cataractous lens proteins showed a remarkable decrease in gamma-, betaB1-, betaA3-, and betaA4-crystallin content, accompanied with some increase in alpha-crystallin (or its aggregate). Higher molecular weight proteins were also observed in the cataractous lenses, with molecular masses which correspond to those of cross-linked dimers (43 to 55 kDa) of beta-crystallins. We consider that the mutation accelerates the aggregation of the crystallins, which is associated with their cross-linking by transglutaminase.