Guanosine 5'-(γ-thio) triphosphate (GTPγS) inhibits phosphorylation of insulin receptor and a novel GTP-binding protein, Gir, from human placenta

Satish Srivastava, Tushar K. Varma, Ashish C. Sinha, Ugra S. Singh

Research output: Contribution to journalArticle

9 Scopus citations


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 G (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.

Original languageEnglish (US)
Pages (from-to)124-128
Number of pages5
JournalFEBS Letters
Issue number1-2
StatePublished - Feb 28 1994



  • G-Protein
  • Insulin receptor
  • Phosphorylation
  • Signal transduction

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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