The Ras protein signals to a number of distinct pathways by interacting with diverse downstream effectors. Among the effectors of Ras are the Raf kinase and RalGDS, a guanine nucleotide dissociation stimulator specific for Ral. Despite the absence of significant sequence similarities, both effectors bind directly to Ras, but with different specificities ...
The Ras protein signals to a number of distinct pathways by interacting with diverse downstream effectors. Among the effectors of Ras are the Raf kinase and RalGDS, a guanine nucleotide dissociation stimulator specific for Ral. Despite the absence of significant sequence similarities, both effectors bind directly to Ras, but with different specificities. We report here the 2.1 A crystal structure of the complex between Ras and the Ras-interacting domain (RID) of RalGDS. This structure reveals that the beta-sheet of the RID joins the switch I region of Ras to form an extended beta-sheet with a topology similar to that found in the Rap-Raf complex. However, the side chain interactions at the joining junctions of the two interacting systems and the relative orientation of the two binding domains are distinctly different. Furthermore, in the case of the Ras-RID complex a second RID molecule also interacts with a different part of the Ras molecule, the switch II region. These findings account for the cross-talk between the Ras and Ral pathways and the specificity with which Ras distinguishes the two effectors.
Related Citations:
Three-Dimensional Structure of the Ras-Interacting Domain of Ralgds Huang, L., Weng, X., Hofer, F., Martin, G.S., Kim, S.H. (1997) Nat Struct Biol 4: 609
Erratum. Three-Dimensional Structure of the Ras-Interacting Domain of Ralgds Huang, L., Weng, X., Hofer, F., Martin, G.S., Kim, S.H. (1997) Nat Struct Biol 4: 840
Activated Ras Interacts with the Ral Guanine Nucleotide Dissociation Stimulator Hofer, F., Fields, S., Schneider, C., Martin, G.S. (1994) Proc Natl Acad Sci U S A 91: 11089
Organizational Affiliation:
Department of Chemistry and E.O. Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA.
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