In vitro alterations similar to posttranslational modification of lens proteins.

Changes similar to posttranslational modifications that are observed with osmotic cataract formation in vivo can be seen with homogenates of lenses. These modifications are the loss of a 31,000 molecular weight (MW) beta crystallin polypeptide, an increase in a 25,000 MW membrane polypeptide. These modifications are potentiated by calcium and occur more rapidly at 37 degrees C than at 4 degrees C. Inhibitors of pepsin or of serine proteases do not influence these modifications, although proteolysis may be responsible for the changes observed.