Ras interaction with two distinct binding domains in Raf-1 may be required for Ras transformation

Jonelle K. Drugan, Roya Khosravi-Far, Michael A. White, Channing J. Der, Ying Ju Sung, Yu Wen Hwan, Sharon L. Campbell

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


Although Raf-1 is a critical Ras effector target, how Ras mediates Raf-1 activation remains unresolved. Raf-1 residues 55-131 define a Ras-binding domain essential for Haf-1 activation. Therefore, our identification of a second Ras-binding site in the Raf-1 cysteine-rich domain (residues 139-184) was unexpected and suggested a more complex role for Ras in Raf-1 activation. Both Ras recognition domains preferentially associate with Ras-GTP. Therefore, mutations that impair Ras activity by perturbing regions that distinguish Has. GDP from Ras-GTP (switch I and II) may disrupt interactions with either Raf-1-binding domain. We observed that mutations of Ras that impaired Ras transformation by perturbing its switch I (T35A and E37G) or switch II (G60A and Y64W) domain preferentially diminished binding to Raf-1- (55-131) or the Haf-1 cysteine-rich domain, respectively. Thus, these Ras- binding domains recognize distinct Ras-GTP determinants, and both may be essential for Ras transforming activity. Finally, since Ha-Ras T35A and E37G mutations prevent Ras interaction with full-length Raf-1, we suggest that Raf-Cys is a cryptic binding site that is unmasked upon Ras interaction with Raf-1-(55-131).

Original languageEnglish (US)
Pages (from-to)233-237
Number of pages5
JournalJournal of Biological Chemistry
Issue number1
StatePublished - Jan 5 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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