Guanosine 5'‐(γ‐thio) triphosphate (GTPγS) inhibits phosphorylation of insulin receptor and a novel GTP‐binding protein, Gir, from human placenta
Open Access
- 28 February 1994
- journal article
- Published by Wiley in FEBS Letters
- Vol. 340 (1-2) , 124-128
- https://doi.org/10.1016/0014-5793(94)80186-x
Abstract
A novel 66 kDa GTP‐binding protein, designated Gir, 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 Gzα (P960). Phosphorylation of IR‐β subunit and Gir 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 Gir at the tyrosine residues. These studies indicate regulation of IR tyrosine kinase activity by guanosine phosphates and involvement of Gir in insulin action.Keywords
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