Epidermal growth factor regulates the exchange rate of guanine nucleotides on p21ras in fibroblasts

László Buday, Julian Downward

Research output: Contribution to journalArticle

100 Citations (Scopus)


Treatment of intact Rat-1 fibroblasts with epidermal growth factor (EGF) leads to rapid activation of cellular ras-encoded proteins. By using the bacterial toxin streptolysin O to permeabilize these cells, it was shown that the low basal rate at which guanine nucleotides bind to, and dissociate from, ras-encoded protein in quiescent fibroblasts was greatly accelerated by EGF treatment. Nucleotide binding to other proteins was not affected. Stimulation of nucleotide exchange on ras-encoded protein required tyrosine kinase but not phospholipase activity. EGF had no effect on total GTPase-activating protein activity. Regulation of ras-encoded protein in Rat-1 fibroblasts is therefore mediated by stimulation, either directly or indirectly, of ras-encoded protein-specific guanine nucleotide exchange factors by the EGF receptor tyrosine kinase.

Original languageEnglish
Pages (from-to)1903-1910
Number of pages8
JournalMolecular and cellular biology
Issue number3
Publication statusPublished - Mar 1993

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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