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. 1990 Aug;87(15):5998–6002. doi: 10.1073/pnas.87.15.5998

Identification of a nucleotide exchange-promoting activity for p21ras.

J Downward 1, R Riehl 1, L Wu 1, R A Weinberg 1
PMCID: PMC54457  PMID: 2116014

Abstract

The biological activity of proteins encoded by the ras family of oncogenes is dependent on whether they are bound to GTP or GDP: the type of nucleotide bound is dependent on the rate of GTP hydrolysis (promoted by the GTPase-activating protein, GAP) and the rate of nucleotide exchange with cytosolic pools. A protein that stimulates the rate of exchange of guanine nucleotide on p21ras has been identified and characterized in cytoplasmic extracts of human placenta. The exchange-promoting protein runs on a gel filtration column with an apparent relative molecular weight of about 60,000. It is sensitive to heat and to trypsin. The exchange-promoting protein acts reversibly and does not cause degradation of p21ras. It is inactive towards the alpha subunit of a heterotrimeric GTP-binding protein (Go alpha) but acts on a large number of different mutant ras proteins, including transforming and effector mutants that are insensitive to the action of GAP. This protein, which we have termed REP (ras exchange-promoting), has the characteristics expected of a physiological activator of p21ras in cellular growth-signal-transduction pathways.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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