Gene and protein structure of a β-crystallin polypeptide in murine lens: Relationship of exons and structural motifs

A 23,000 molecular weight β-crystallin (β23) of the murine lens is encoded in a 4.1 ± 0.3-kilobase gene containing three introns. Each of the four exons seems to code for a separate structural motif of the protein, whose tertiary structure was predicted by an interactive computer graphics technique based on the crystallographic structure of bovine γ(II)-crystallin. The first exon also encodes a hydrophobic N-terminal peptide resembling membrane anchor sequences of other proteins. Our results indicate structural homology among the β- and γ-crystallin polypeptides, and link gene structure with protein structure in this superfamily of lens proteins.