The in vivo phosphorylation sites of bovine αB‐crystallin

Abstract

Phosphate content determinations established that in αB‐crystallin two phosphate groups can be present in vivo in bovine lenses. Comparison of tryptic digests of phosphorylated and unphosphorylated αB chains, revealed the location of the two phosphorylation sites in tryptic peptides T2 and T3. Thermolytic digestion and gas‐phase sequencing demonstrated that Ser‐19 and Ser‐45 are the in vivo phosphorylation sites of bovine αB‐crystallin. This pattern of phosphorylation differs from the previously reported in vitro obtained results.