Cleavage from the N-terminal region of βBp 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 βBp crystallin. Both antiβBp_1-12 and anti-βBp_195-204 recognize specifically the βBp component of bovine lens. In the young human lens, anti-βBp_195-204 recognizes predominantly the 26000 MW form of βBp, while in older lenses this same antiserum recognizes mainly the 22000 MW in vivo proteolysis product. In contrast, during aging of the normal human lens anti-βBp_1-12 recognizes only decreasing amounts of the 26000 MW form of βBp, with no binding to the 22000 MW form of this polypeptide. These results suggest that during aging of the normal human lens, the N-terminus of βBp is the preferred site of in vivo proteolysis.