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Insulin-like growth factor (IGF)-I receptor purified from human placental membranes as previously described (LeBon, T. R., Jacobs, S., Cuatrecasas, P., Kathuria, S., and Fujita-Yamaguchi, Y. (1986) J. Biol. Chem. 261, 7685-7689) was characterized. The IGF-I receptor was similar to the insulin receptor with respect to subunit structure (beta-alpha-alpha-beta), apparent sizes of deglycosylated alpha (Mr = approximately 88,000) and beta (Mr = approximately 67,000) subunits, and amino acid composition of the subunits. Monoclonal antibody specific to each receptor recognized its own receptor whereas polyclonal anti-human insulin receptor antibody cross-reacted with the IGF-I receptor, indicating that the receptors share one or more antigenic sites. Further characterization of the purified IGF-I receptor tyrosine-protein kinase activity indicated that by analogy with the insulin receptor the monomeric alpha beta form of the IGF-I receptor appears to have higher kinase activity than the intact receptor in the alpha 2 beta 2 form. The most significant difference between the two receptors was found in the N-terminal amino acid sequences of their alpha subunits, which apparently show 60% identity. The IGF-I receptor alpha subunit lacks residues corresponding to the N-terminal 4 amino acids of the insulin receptor alpha subunit. These results provide the first direct proof that the IGF-I receptor is a molecule distinct from the insulin receptor despite numerous similarities.
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
August 1986,
Biochemical and biophysical research communications,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
September 1983,
The Journal of biological chemistry,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
February 1991,
Biochemical Society transactions,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
September 1995,
German journal of ophthalmology,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
September 1984,
Endocrinology,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
January 1991,
Hormone research,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
October 1990,
The Journal of biological chemistry,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
March 1993,
The Biochemical journal,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
July 1990,
Domestic animal endocrinology,
Y Fujita-Yamaguchi, and
T R LeBon, and
M Tsubokawa, and
W Henzel, and
S Kathuria, and
D Koyal, and
J Ramachandran
February 1987,
Biochemical and biophysical research communications,
