Src promotes GTPase activity of Ras via tyrosine 32 phosphorylation

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 36; pp. E3785 - E3794
• Main Authors: Bunda, Severa, Heir, Pardeep, Srikumar, Tharan, Cook, Jonathan D., Burrell, Kelly, Kano, Yoshihito, Lee, Jeffrey E., Zadeh, Gelareh, Raught, Brian, Ohh, Michael
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.09.2014; National Acad Sciences
• Series: PNAS Plus
• Subjects: Amino Acid Sequence; Animals; Biological Sciences; Cancer; Cell Line; Crystallography; Eukaryotes; GTP Phosphohydrolases - chemistry; GTP Phosphohydrolases - metabolism; GTPase-Activating Proteins - metabolism; guanosine triphosphate; Guanosine Triphosphate - metabolism; guanosinetriphosphatase; Humans; Hydrolysis; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Mice; Models, Molecular; Molecular Sequence Data; Mutant Proteins - metabolism; Mutation; Phosphorylation; Phosphotyrosine - metabolism; PNAS Plus; Protein Binding; Proteins; raf Kinases - metabolism; src-Family Kinases - metabolism; tyrosine
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1406559111

Significance Despite the well-established connection between Ras and Src, there currently is no evidence of direct interaction between these two proteins. We show here that Src binds to and phosphorylates GTP-loaded Ras on a conserved Y32 residue within the switch I region. It has been shown that Raf binds to Ras with an affinity 1,000-fold greater than that of GAP. However, it has remained unclear how GAP is able to outcompete Raf for Ras upon Raf displacement. We show here that Y32 phosphorylation inhibits Raf binding to Ras and concomitantly promotes GAP association and GTP hydrolysis, thereby ensuring unidirectionality to the Ras GTPase cycle. These findings reveal new fundamental mechanistic insight into how Src negatively regulates Ras.