Isolation and characterization of the 1 to 49 amino-terminal sequence of pro-opiomelanocortin from bovine posterior pituitaries.

An amino-terminal fragment of pro-opiomelanocortin (POMC) has been isolated from bovine intermediate pituitaries by reversed-phase high-performance liquid chromatography. Peptide mapping and amino acid analysis indicated that the primary sequence corresponds exactly to that predicted by cDNA techniques for the first 49 residues of POMC including the presence of four cysteine residues. This peptide is almost certainly generated together with the gamma-melanotropins during the biosynthetic processing of the 16K amino-terminal fragment of bovine POMC. Careful analysis of the fragments resulting from V8 protease and trypsin digestion has permitted assignment of cystine bridges between residues 2 and 24 and between residues 8 and 20.