Increased cleavage of the c-terminal serine from alpha-A crystallin present in the high molecular weight aggregate fraction from human and bovine lenses

Abstract

PURPOSE. To determine the relative amount of serine-173 cleavage from the C-terminus of alpha-A crystallin from the high molecular weight aggregate fraction and lower molecular weight alpha crystallin fraction from water soluble proteins of human and bovine lenses. METHODS. Using gel permeation chromatography, the high molecular weight aggregate fraction and lower molecular weight alpha crystallin fractions were purified from soluble proteins of human lenses and mature bovine lenses. Alpha-A crystallin present in these fractions was digested with trypsin, followed by the use of reverse phase chromatography and synthetic peptide standards to identify and quantitate the relative amount of in vivo cleavage of C-terminal serine –173. RESULTS. For all human and bovine lenses studied, alpha-A crystallin in the high molecular weight aggregate fraction had undergone more truncation at the C-terminus, than the alpha-A crystallin present in the lower molecular weight alpha crystallin fraction from the same lens. CONCLUSIONS. Relative to the alpha-A crystallin present in the lower molecular weight alpha fraction, the alpha-A crystallin present in the high molecular weight aggregate fraction from the same human and bovine lenses has undergone increased cleavage of the C-terminal serine residue, suggesting a common mechanism that may contribute towards formation of protein aggregation in vivo.