CED-5/CED-12 (DOCK/ELMO) can promote and inhibit F-actin formation via distinct motifs that target different GTPases.

protein structures suggested a putative GAP region, which we mutated to show that CED-12 likely functions as a GAP. Genetic and gene expression tests identify other GTPases, CDC-42 and RHO-1, regulated by this newly uncovered CED-12 GAP function. This places CED-5/CED-12 at a central position, where it can support the cycling of multiple GTPases, and both promote and inhibit F-actin nucleation.