title: Sequences of liver cDNAs encoding two different mouse insulin-like growth factor I precursors.
abstract: Complementary DNAs encoding mouse liver insulin-like growth factor I (IGF-I) have been isolated and sequenced. Alternative RNA splicing results in the synthesis of two types of mouse IGF-I precursor that differ in the size and sequence of the COOH-terminal peptide. The sequences of the signal peptides, IGF-I moieties and the first 16 amino acids of the COOH-terminal peptides or E-domains of the two precursors are identical. The sequence difference results from the presence in preproIGF-IB mRNA of a 52 base insertion which introduces a 17 amino acid segment into the COOH-terminal peptide of preproIGF-IB and also causes a shift in the reading frame of the mRNA. As a consequence of this insertion, the COOH-terminal 19 and 25 amino acids of mouse preproIGF-IA and -IB, respectively, are different. The sequences of mouse and human preproIGF-IA are highly conserved and possess 94% identity. In contrast, the sequences of mouse and human preproIGF-IB are quite different in the region of the COOH-terminal peptide. A comparison of the sequences of mouse and human preproIGF-IB mRNA indicates that they are generated by different molecular mechanisms.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008099:Liver / Q000502:physiology; D051379:Mice; D011498:Protein Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013002:Somatomedins / Q000235:genetics*
chemical_list: D011498:Protein Precursors; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D004247:DNA