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Guanosine 5'‐(γ‐thio) triphosphate (GTPγS) inhibits phosphorylation of insulin receptor and a novel GTP‐binding protein, G ir , from human placenta
Author(s) -
Srivastava Satish K.,
Varma Tushar K.,
Sinha Ashish C.,
Singh Ugra S.
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)80186-x
Subject(s) - gtp' , guanosine , g protein , phosphorylation , biochemistry , tyrosine phosphorylation , insulin receptor , tyrosine , chemistry , microbiology and biotechnology , biology , signal transduction , insulin , endocrinology , enzyme , insulin resistance
A novel 66 kDa GTP‐binding protein, designated G ir , has been partially purified along with insulin receptor (IR) from human placenta. This protein binds 8‐azido‐GTP, is ADP‐ribosylated by pertussis toxin, phosphorylated by IR tyrosine kinase and cross‐reacts with antibodies against synthetic peptides from the GTP‐binding domain of G zα (P960). Phosphorylation of IR‐β subunit and G ir by IR tyrosine kinase was almost completely inhibited by 100 μM GTPγS, >75% by 50 μM and 20–30% by 1 μM, while GDP at these concentrations had no significant effect on the phosphorylation. IR tyrosine kinase phosphorylated G ir at the tyrosine residues. These studies indicate regulation of IR tyrosine kinase activity by guanosine phosphates and involvement of G ir in insulin action.