Exon duplication and divergence in the human preproglucagon gene.

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152

作者：

GI Bell，R Sanchez-Pescador，PJ Laybourn，RC Najarian

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摘要：

Glucagon is a 29-amino acid pancreatic hormone which counteracts the blood glucose-lowering action of insulin by stimulating hepatic glycogenolysis and gluconeogenesis 1 . The structure of the hamster pancreatic glucagon precursor has recently been determined from the sequence of a cloned cDNA 2 . Hamster preproglucagon is a 180-amino acid protein which contains five functional regions; a signal or pre-peptide, an NH 2 -terminal peptide (also called glicentin-related pancreatic peptide, GRPP), glucagon and two carboxy-terminal glucagon-like peptides (GLP-1 and GLP-2). The sequences of two non-allelic anglerfish pancreatic glucagon precursors 3–5 have also been determined and their organization is similar but not identical to the hamster protein; they lack the polypeptide segment corresponding to hamster GLP-2. The presence of three regions possessing internal homology, that is, glucagon, GLP-1 and GLP-2, within proglucagon and the absence of GLP-2 in the anglerfish precursors suggests that the structure of the preproglucagon gene might provide insight into the evolution of this polyprotein. We have isolated and sequenced the human preproglucagon gene and report here that the organization of the human precursor deduced from this sequence is identical to the hamster protein. The gene contains at least three intervening sequences which divide the protein-coding portion of the gene into four regions corresponding to the signal peptide and part of the NH 2 -terminal peptide, the remainder of the NH 2 -terminal peptide and glucagon, GLP-1 and GLP-2. The data suggest that triplication and subsequent sequence divergence of an exon encoding glucagon or a glucagon-like peptide produced this polyprotein precursor.

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关键词：

Animals Humans Glucagon Insulin Proinsulin Protein Precursors Base Sequence Amino Acid Sequence Proglucagon Cricetinae