MOLECULAR-CLONING OF A CDNA-ENCODING PROGLUCAGON FROM GOLDFISH, CARASSIUS-AURATUS

Proglucagon is the precursor for a number of peptides: glucagon and at least one glucagon-like peptide (GLP1 and GLP2). The production of th ese peptides is regulated by tissue-specific proteolytic processing. A cDNA encoding the proglucagon in goldfish was characterized using rap id amplification of the cDNA ends. Goldfish proglucagon cDNA was found to be 660 base pair long, encoding a putative 121-residue prepro-horm one. Goldfish glucagon and GLP do not terminate with two basic residue s, as is common in vertebrates as specific endopeptidase cleavage reco gnition site. Instead, only one basic residue is found at these positi ons. It is not known whether goldfish glucagon and GLP have adopted an alternate processing pathway, or whether they remained unprocessed to yield C-terminal-extended peptides. By reverse transcriptase-polymera se chain reaction, the proglucagon mRNA was found to be expressed main ly in the gall bladder region and the proximal intestine, and less in the spleen and distal intestine.