IDENTIFICATION OF THE IN-VIVO TRUNCATION SITES AT THE C-TERMINAL REGION OF ALPHA-A CRYSTALLIN FROM AGED BOVINE AND HUMAN LENS

Total alpha-A crystallin was purified from young Versus old lens, followed by digestion with cyanogen bromide. Laser desorption mass spectrometry of the C-terminal fragment demonstrated age-dependent loss of one and five amino acids from the C-terminus of alpha-A crystallin from both bovine and human lens. These results demonstrate specific peptide bonds of alpha-A crystallin are cleaved during the aging process of the normal lens. The C-terminal region is cleaved in two places between the two hydroxyl-containing amino acids present in the sequence -P-S(T)-S-.