Abstract
In an attempt to further investigate the structure of the Somatomedins/Insulin-like Growth Factors (SM/IGF), especially the possible existence of precursor peptides and their structural relation to the circulating forms, we have used recombinant-DNA techniques to identify and isolate cDNA-clones encoding human IGF-I and -II.
By screening an adult human liver cDNA-library with a synthetic oligonucleotide, we initially isolated a cDNA encoding the 70 amino acids of IGF-I preceded by an N-terminal peptide of at least 25 amino acids and a carboxyl-terminal peptide of 35 amino acids, thus demonstrating that IGF-I is synthesized as a precursor. Subsequently, by cross-hybridizing the cDNA-library with restriction fragments of this cDNA we were able to isolate another cDNA clone, encoding the 67 amino acids of IGF-II, flanked by nucleotide sequences encoding a highly hydrophobic leader peptide and a carboxyl-terminal peptide.
These results provide solid evidence that both IGF-I and IGF-II are synthesized as precursor proteins and that formation of IGF-I and IGF-II from these precursors requires proteolytic processing at both the N-terminal and the C-terminal ends.
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Jansen, M., Van Tol, H., Van Schaik, F. et al. Human insulin-like growth factors I and II (IGF-I, IGF-II) are synthesized as precursors. Pediatr Res 18, 1206 (1984). https://doi.org/10.1203/00006450-198411000-00034
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DOI: https://doi.org/10.1203/00006450-198411000-00034
