Primary Structure of the Bovine β-Crystallin Bp Chain Internal Duplication and Homology with y-Crystallin.

The major polypeptide chain of bovine β-crystallin, βBp, was fragmented by means of cyanogen bromide treatment and by enzymatic digestions. Manual and automated Edman degradation of the resulting peptides provided the complete amino acid sequence of the βBp chain. The N-terminal alanine residue was shown to be N-α-acetylated by mass spectrometry. The chain has a length of 204 residues and a calculated molecular weight of 23 210. There is a considerable degree of homology between the N-terminal and C-terminal halves of the chain, presumably reflecting a tandem duplication of a shorter ancestral gene. The sequence of βBp is sufficiently related to that of γ-crystallin II to place these proteins in the same superfamily. No sequence relationship was found with the α-crystallin chains. [ABSTRACT FROM AUTHOR]