title: How Vav proteins discriminate the GTPases Rac1 and RhoA from Cdc42.
abstract: Vav proteins are GDP/GTP exchange factors for Rho/Rac GTPases that are activated by tyrosine phosphorylation. These proteins activate Rac1, RhoG, and RhoA but not the highly related Cdc42 protein. At present, there is no available information to explain this substrate selectivity at the structural level. Here we show that the selection of Vav proteins substrates is achieved at two different levels. On one hand, Vav proteins utilize some residues of the beta2/beta3 region of Rho/Rac GTPases (D49 and E54) to assure the specific binding to its substrate. In addition, these exchange factors need a second structural signal located in the beta5 region of Rho/Rac proteins (residue K118) to promote proper GDP/GTP exchange. These results identify the amino acid residues that allow the discrimination of the Vav family substrates from Cdc42 and, in addition, demonstrate that the activation of specific Rho/Rac GTPases by these GEFs requires two concatenated events, binding and subsequent enzyme reaction, whose specificities are determined by two separate regions of Rho proteins.
authors.affiliation: Centro de Investigación del Cáncer, University of Salamanca-CSIC, 37007 Salamanca, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Movilla
authors.forename: M
authors.initials: M
authors.lastname: Dosil
authors.forename: Y
authors.initials: Y
authors.lastname: Zheng
authors.forename: X R
authors.initials: XR
authors.lastname: Bustelo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017354:Point Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D020764:cdc42 GTP-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein