Cleavage from the N-terminal region of beta Bp crystallin during aging of the human lens.

Polyclonal antisera have been made to synthetic peptides that correspond to the N-terminal (residues 1-12) and C-terminal (residues 195-204) sequences of bovine beta Bp crystallin. Both anti-beta Bp1-12 and anti-beta Bp195-204 recognize specifically the beta Bp component of bovine lens. In the young human lens, anti-beta Bp195-204 recognizes predominantly the 26,000 MW form of beta Bp, while in older lenses this same antiserum recognizes mainly the 22,000 MW in vivo proteolysis product. In contrast, during aging of the normal human lens anti-beta Bp1-12 recognizes only decreasing amounts of the 26,000 MW form of beta Bp, with no binding to the 22,000 MW form of this polypeptide. These results suggest that during aging of the normal human lens, the N-terminus of beta Bp is the preferred site of in vivo proteolysis.