Abstract
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 language | English (US) |
---|---|
Pages (from-to) | 233-237 |
Number of pages | 5 |
Journal | Journal of Biological Chemistry |
Volume | 271 |
Issue number | 1 |
DOIs | |
State | Published - Jan 5 1996 |
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology