THE CONFORMATION FORMED BY THE DOMAIN AFTER ALANINE-155 INDUCES INVERSION OF ASPARTIC ACID-151 IN ALPHA-A-CRYSTALLIN FROM AGED HUMAN LENSES

A new cleavage site, which is a post-translational modification, was f ound between residues His-154 and Ala-155 in alpha A-crystallin hom th e aged human lens. After trypsin digestion of alpha A-crystallin two p eptides that include Asp-151 were obtained and have remarkable differe nces. That is, the stereo-configuration of the Asp-151 in the normal l ength peptide was predominately inverted to the D-isomer of beta-aspar tyl form (D/L of 5.7), However, the stereoconfiguration of the Asp-151 in the cleavage peptide, that lacks the sequence following Ala-155 to the C-terminus, remained predominately in the L-isomer form as indica ted by a D/L value of 0.3. The results suggest that the secondary stru cture in the region of Ala-155 to the C-terminus may constitute a held that causes the inversion of the Asp-151 to the D-isomer form, Since this kind of cleavage was not found in alpha A-crystallin from young l ens, the cleavage between His-154 and Ala-155 is probably the result o f aging. (C) 1997 Academic Press.