title: Molecular basis for Rac1 recognition by guanine nucleotide exchange factors.
abstract: Rho GTPases are activated by a family of guanine nucleotide exchange factors (GEFs) known as Dbl family proteins. The structural basis for how GEFs recognize and activate Rho GTPases is presently ill defined. Here, we utilized the crystal structure of the DH/PH domains of the Rac-specific GEF Tiam1 in complex with Rac1 to determine the structural elements of Rac1 that regulate the specificity of this interaction. We show that residues in the Rac1 beta2-beta3 region are critical for Tiam1 recognition. Additionally, we determined that a single Rac1-to-Cdc42 mutation (W56F) was sufficient to abolish Rac1 sensitivity to Tiam1 and allow recognition by the Cdc42-specific DH/PH domains of Intersectin while not impairing Rac1 downstream activities. Our findings identified unique GEF specificity determinants in Rac1 and provide important insights into the mechanism of DH/PH selection of GTPase targets.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599, USA.
authors.forename: A E
authors.initials: AE
authors.lastname: Karnoub
authors.forename: D K
authors.initials: DK
authors.lastname: Worthylake
authors.forename: K L
authors.initials: KL
authors.lastname: Rossman
authors.forename: W M
authors.initials: WM
authors.lastname: Pruitt
authors.forename: S L
authors.initials: SL
authors.lastname: Campbell
authors.forename: J
authors.initials: J
authors.lastname: Sondek
authors.forename: C J
authors.initials: CJ
authors.lastname: Der
mesh_terms: D016475:3T3 Cells; D033942:Adaptor Proteins, Vesicular Transport; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D002471:Cell Transformation, Neoplastic; D004789:Enzyme Activation; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013379:Substrate Specificity; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D020764:cdc42 GTP-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; D020662:Guanine Nucleotide Exchange Factors; D008024:Ligands; D011506:Proteins; D011993:Recombinant Fusion Proteins; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; C513260:Tiam1 protein, mouse; C115919:intersectin 1; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein