The Rac1-binding domain is the C-terminal portion of YpkA from Yersinia. It is an all-helical molecule consisting of two distinct subdomains connected by a linker. the N-terminal end, residues 434-615, consists of six helices organized into two three-helix bundles packed against each other. This region is involved with binding to GTPases. The C-terminal end, residues 705-732. is a novel and elongated fold consisting of four helices clustered into two pairs, and this fold carries the helix implicated in actin activation. Rac1-binding domain mimics host guanidine nucleotide dissociation inhibitors (GDIs) of the Rho GTPases, thereby inhibiting nucleotide exchange in Rac1 and causing cytoskeletal disruption in the host. It is usually found downstream of pfam00069.