Definition and comparison of the phosphorylation sites of the A and B chains of bovine alpha-crystallin.
The major phosphorylation sites of bovine alpha-crystallin Ser122 in the A chain, Ser59 and Ser43 and/or Ser45 in the B chain have been previously characterized. Further analysis of total alpha-crystallin, isolated from the cortex of calf lenses incubated in the presence of [32P]orthophosphate, demonstrated the presence of additional phosphorylation sites in both chains. At least three additional phosphorylation sites were found in the A chain and at least one in the B chain. These additional sites accounted for approximately 25% of the radioactivity incorporated in the protein. Two general sequences were found in most phosphorylation sites of both chains of alpha-crystallin: (Arg/Lys)-(X)-Pro-Ser and Ser-(X)-Ser-Leu-Ser. In spite of the 57% homology in the sequences of the A and B chains, the phosphorylation sites are located, in the A polypeptide, at the C-terminal third and in the B polypeptide, at the N-terminal third. The alignment of the regions containing the phosphorylation sites of both chains (C-terminal third of the A and N-terminal third of the B chain) revealed an unexpected similarity in the relative positions of the sites in each chain.
Chiesa
R
R
Department of Ophthalmology, College of Physicians and Surgeons, Columbia University, New York, NY 10032.
Gawinowicz-Kolks
M A
MA
Kleiman
N J
NJ
Spector
A
A
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003459:Crystallins / Q000378:metabolism*; D004586:Electrophoresis; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation
D003459:Crystallins