National Center for
3OC5: Crystal Structure Of The Vibrio Cholerae Secreted Colonization Factor Tcpf
Crystal Structure of the Vibrio cholerae Colonization Factor TcpF and Identification of a Functional Immunogenic Site
J. Mol. Biol. (2011)
Vibrio cholerae relies on two main virulence factors-toxin-coregulated pilus (TCP) and cholera toxin-to cause the gastrointestinal disease cholera. TCP is a type IV pilus that mediates bacterial autoagglutination and colonization of the intestine. TCP is encoded by the tcp operon, which also encodes TcpF, a protein of unknown function that is secreted by V. cholerae in a TCP-dependent manner. Although TcpF is not required for TCP biogenesis, a tcpF mutant has a colonization defect in the infant mouse cholera model that is as severe as a pilus mutant. Furthermore, TcpF antisera protect against V. cholerae infection. TcpF has no apparent sequence homology to any known protein. Here, we report the de novo X-ray crystal structure of TcpF and the identification of an epitope that is critical for its function as a colonization factor. A monoclonal antibody recognizing this epitope is protective against V. cholerae challenge and adds to the protection provided by an anti-TcpA antibody. These data suggest that TcpF has a novel function in V. cholerae colonization and define a region crucial for this function.