Coupling of Ras and Rac guanosine triphosphatases through the Ras exchanger Sos

  • Nimnual A
  • Yatsula B
  • Bar-Sagi D
  • 62


    Mendeley users who have this article in their library.
  • 352


    Citations of this article.


The Son of Sevenless (Sos) proteins control receptor-mediated activation of Ras by catalyzing the exchange of guanosine diphosphate for guanosine triphosphate on Ras. The NH2-terminal region of Sos contains a Dbl homology (DH) domain in tandem with a pleckstrin homology (PH) domain. In COS-1 cells, the DH domain of Sos stimulated guanine nucleotide exchange on Rac but not Cdc42 in vitro and in vivo. The tandem DH-PH domain of Sos (DH-PH-Sos) was defective in Rac activation but regained Rac stimulating activity when it was coexpressed with activated Ras. Ras-mediated activation of DH-PH-Sos did not require activation of mitogen-activated protein kinase but it was dependent on activation of phosphoinositide 3-kinase. These results reveal a potential mechanism for coupling of Ras and Rac signaling pathways.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document


  • Anjaruwee S. Nimnual

  • Bogdan A. Yatsula

  • Dafna Bar-Sagi

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free