title: Sequence of cDNA encoding human insulin-like growth factor I precursor.
abstract: Somatomedins (SM) or insulin-like growth factors (IGF) constitute a heterogeneous group of peptides with important growth-promoting effects in vitro as well as in vivo. Amino acid sequences have been determined for only two of them, IGF-I and IGF-II, which are highly homologous. IGF-I, which is identical with SM-C, is composed of 70 amino acid residues and IGF-II contains 73 amino acids and may be identical with SM-A. Other peptides with different charge properties but with similar SM-like or insulin-like behaviour in biological and receptor assays, have been described but have not yet been fully characterized. The liver is known to be a major site of production of these peptides, but many other tissues--especially in the fetus--may synthesize them as well. We report here the nucleotide sequence of a human liver cDNA encoding the complete amino acid sequence of IGF-I. The IGF-I coding region is flanked by sequences encoding an amino-terminal peptide of at least 25 amino acid residues and a carboxyl-terminal peptide of 35 amino acids. This provides evidence that IGF-I is synthesized as a precursor protein and that formation of IGF-I from this precursor requires proteolytic processing at both ends.
mesh_terms: D001483:Base Sequence; D004247:DNA; D006801:Humans; D007328:Insulin / Q000235:genetics*; D010455:Peptides / Q000235:genetics*; D011498:Protein Precursors / Q000235:genetics*; D013002:Somatomedins / Q000235:genetics*
chemical_list: D007328:Insulin; D010455:Peptides; D011498:Protein Precursors; D013002:Somatomedins; D004247:DNA