Alpha-a crystalline quantitation of c-terminal modification during Lens aging

Previous studies have demonstrated that the C-terminal region of alpha-A crystallin is susceptible to age-dependent, posttranslational modification. To quantitate the amount of modification, alpha-A crystallin was purified from total proteins of the aging bovine lens, then digested with lys-C endoproteinase. Reverse phase, high pressure liquid chromatography was used to resolve and quantitate the resulting peptides, to determine the amount of C-terminal peptide relative to peptides from other regions of the protein that have not been reported to undergo modification. The results indicate that relative to alpha-A crystallin from newborn lens, posttranslational modification has occurred in approximately 45-55% of the C-terminal region from mature lens. These results demonstrate extensive modification of the C-terminal region of alpha-A crystallin from the mature lens, indicating that during the aging process, posttranslational modifications in this region may make significant contributions to the aggregated state and/or molecular chaperone properties of the molecule. Curr. Eye Res. 13: 879-883, 1994. © 1994 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.