Crystal Structure of the Hexameric Traffic ATPase of the Helicobacter pylori Type IV Secretion System

The type IV secretion system of Helicobacter pylori consists of 10–15 proteins responsible for transport of the transforming protein CagA into target epithelial cells. Secretion of CagA crucially depends on the hexameric ATPase, HP0525, a member of the VirB11-PulE family. We present the crystal structure of a binary complex of HP0525 bound to ADP. Each monomer consists of two domains formed by the N- and C-terminal halves of the sequence. ADP is bound at the interface between the two domains. In the hexamer, the N- and C-terminal domains form two rings, which together form a chamber open on one side and closed on the other. A model is proposed in which HP0525 functions as an inner membrane pore, the closure and opening of which is regulated by ATP binding and ADP release.