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 organised 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 [1]. It is usually found downstream of Pfam:PF00069.

1: Yersinia virulence depends on mimicry of host Rho-family nucleotide dissociation inhibitors. Prehna G, Ivanov MI, Bliska JB, Stebbins CE; Cell. 2006;126:869-880. PMID:16959567