The Ras homology (Rho) guanine nucleotide exchange factor p115-RhoGEF couples the α 1 3 heterotrimeric guanine nucleotide binding protein (G protein) subunit to Rho GTPase. α 1 3 binds to a regulator of G protein signaling (RGS) domain in p115-RhoGEF, but the mechanism of α 1 3 activation of p115-RhoGEF is poorly understood. In this report, we demonstrate in cell-based assays that the acidic-rich N-terminus, adjacent to the RGS domain, is required for binding to activated α 1 3 , and refine the importance of this region by showing that mutation of glutamic acids 27 and 29 in full-length p115-RhoGEF is sufficient to prevent interaction with activated α 1 3 . However, α 1 3 -interacting deficient N-terminal mutants of p115-RhoGEF retain α 1 3 -dependent plasma membrane recruitment. Overall, these findings demonstrate a critical role for the N-terminal extension of p115-RhoGEF in mediating binding to α 1 3 and dissociate two activities of p115-RhoGEF: binding to activated α 1 3 and translocation to the PM in response to activated α 1 3 .