A NOVEL PARTNER FOR THE GTP-BOUND FORMS OF RHO AND RAC

Using the yeast two hybrid system and overlay assays me identified a p utative rholrac effector, citron, which interacts with the GTP-bound f orms of rho and rac1, but not with cdc42. Extensive homologies to know n proteins were not observed. This 183 kDa protein contains a C6H2 zin c finger, a PH domain, and a long coiled-coil forming region including 4 leucine zippers and the rholrac binding site, We recently identifie d three others putative rho effecters characterized by a common rho bi nding motif. Citron does not share this motif and displays a distincti ve protein organization, thus defining a separate class of rho partner s.