Amino-Terminal Sequences of Two Polypeptides from Human Serum with Nonsuppressible Insulin-Like and Cell-Growth-Promoting Activities: Evidence for Structural Homology with Insulin B Chain

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 73; no. 12; pp. 4379 - 4381
• Main Authors: Rinderknecht, Ernst, Humbel, René E.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01.12.1976; National Acad Sciences
• Subjects: Amino Acid Sequence; Amino acids; Autoanalysis; Biochemistry; Cell growth; Growth Substances - analysis; Human growth; Humans; Insulin; Insulin - analysis; Insulin like effects; Molecules; Nonsuppressible Insulin-Like Activity - analysis; Sequencing; Somatomedins; Tuna
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.73.12.4379

The amino-terminal sequences of two polypeptides with nonsuppressible insulin-like and cell-growth-promoting activities (NSILA I and II), isolated from human serum, were determined. Of the first 31 residues, 22 are identical in NSILA I and II. Moreover, a striking structural similarity was found between NSILA and insulin B chain: 47 and 57% of residues 1-30 in NSILA I are identical to those in insulin B chain from man and tuna fish, respectively. This high degree of sequence identity is presented as evidence for homology and thus for a common evolutionary origin of insulin and NSILA. Based on these results and on biological properties of NSILA described earlier, a new designation for NSILA is proposed: insulin-like growth factor (IGF).