Two Structurally Closely Related Polypeptides Encoded by 14-S mRNA Isolated from Rat Lens

Abstract

14-S mRNA from rat lens codes for 2 subunits of .alpha.-crystallin, A2 (MW 20,000) and AIns (MW 24,000, previously referred to as .alpha.X). The structural relationship between both translation products was proved by immunoprecipitation with antisera directed against the different crystallin classes. Competition immunoprecipitation showed that the 14-S mRNA translation products are precipitated by common antibodies, specific for the A subunit of .alpha.-crystallin. Two-dimensional gel electrophoresis and peptide analysis provided further evidence that the 24,000-MW polypeptide synthesized in vitro under direction of 14-S mRNA is identical with native .alpha.AIns. Although the structures of .alpha.A2 and .alpha.AIns are very similar, no precursor-product relationship exists between the 14-S-mRNA-encoded polypeptides.