The molecular cloning of the chromogranin A-like precursor of beta-granin and pancreastatin from the endocrine pancreas.

The cDNA encoding the precursor form of the chromogranin A-related proteins, beta-granin and pancreastatin, was obtained by immune screening of rat insulinoma and pancreatic islet cDNA libraries. The sequence was virtually identical to that of rat adrenal chromogranin A, suggesting that the different molecular forms of chromogranin A immunoreactivity found in adrenal medulla and endocrine pancreas are related to differences in post-translational proteolytic processing. The rat chromogranin A, unlike its bovine and human counterparts, contained a 20-residue glutamine sequence inserted within the N-terminal beta-granin sequence. Although the encoding CA(G/A) repeat recurs frequently in the rat genome, the rat chromogranin A molecule appears to be the product of a single gene and mRNA transcript.