The toxin-coregulated pilus (TCP) of Vibrio cholerae and the soluble TcpF protein that is secreted via the TCP biogenesis apparatus are essential for intestinal colonisation in the disease of cholera. TcpQ is part of an outer membrane complex of the TCP biogenesis apparatus, comprised of TcpC and TcpQ, and the TcpQ is required for proper localisation of TcpC to the outer membrane. The domain is found in other Proteobacterial species apart from Vibrio.

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2: Identification of a TcpC-TcpQ outer membrane complex involved in the biogenesis of the toxin-coregulated pilus of Vibrio cholerae. Bose N, Taylor RK; J Bacteriol. 2005;187:2225-2232. PMID:15774863