Biochemical analysis of regulation of Vav, a guanine-nucleotide exchange factor for Rho family of GTPases

Publisher Summary This chapter discusses the biochemical analysis of regulation of Vav, a guanine-nucleotide exchange factor for Rho family of guanosine 5'-triphosphate (GTPase). Ras and Rac GTPases are activated by guanine-nucleotide exchange factors (GEFs) related to the Saccharomyces cerevisiae CDC25 gene product and the Dbl oncoprotein, respectively. Several Ras-GEFs have been described, whereas more than 20 proteins structurally related to the catalytic domain of Dbl have been reported. Vertebrate Ras-GEFs are generally bifunctional molecules possessing both a CDC25-related domain and a Dbl homology (DH) domain. Thus, Ras-GEFs have the potential to activate Ras and Rac family members. For those Dbl-related molecules where GEF activity has been detected, this activity is specific for one or more of the Rho family GTPases. However, many of the Dbl-related molecules (including Vav), when expressed as recombinant proteins, fail to stimulate the release of GDP from Rho proteins in vitro . The chapter describes the biochemical analysis of Vav and the events contributing to the activation of its Rho family-specific GEF activity.