title: Structure of the G60A mutant of Ras: implications for the dominant negative effect.
abstract: Substituting alanine for glycine at position 60 in v-H-Ras generated a dominant negative mutant that completely abolished the ability of v-H-Ras to transform NIH 3T3 cells and to induce germinal vesicle breakdown in Xenopus oocytes. The crystal structure of the GppNp-bound form of RasG60A unexpectedly shows that the switch regions adopt an open conformation reminiscent of the structure of the nucleotide-free form of Ras in complex with Sos. Critical residues that normally stabilize the guanine nucleotide and the Mg(2+) ion have moved considerably. Sos binds to RasG60A but is unable to catalyze nucleotide exchange. Our data suggest that the dominant negative effect observed for RasG60A.GTP could result from the sequestering of Sos in a non-productive Ras-GTP-guanine nucleotide exchange factor ternary complex.
authors.affiliation: Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661, USA.
authors.forename: Bradley
authors.initials: B
authors.lastname: Ford
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Skowronek
authors.forename: Sean
authors.initials: S
authors.lastname: Boykevisch
authors.forename: Dafna
authors.initials: D
authors.lastname: Bar-Sagi
authors.forename: Nicolas
authors.initials: N
authors.lastname: Nassar
mesh_terms: D000409:Alanine / Q000235:genetics; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D003461:Crystallography; D005998:Glycine / Q000235:genetics; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D015689:Oncogene Protein p21(ras) / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D009865:Oocytes; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014981:Xenopus
chemical_list: D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D015689:Oncogene Protein p21(ras); D000409:Alanine; D005998:Glycine