The toxin-coregulated pilus (TCP) and cholera toxin (CT) are two main virulence factors produced by V. cholerae, which allows the bacterium to colonize and establish an infection in a host and to cause the physical symptoms of the disease, respectively. Increased expression of the TCP, a type IV pilus expressed by the tcp operon (tcpABQCRDSTEF) located on the Vibrio pathogenicity island (VPI), has been associated with enhanced attachment and is essential for colonization of the intestinal epithelium [1]. This domain of unknown function is found in TcpS proteins in Vibrionaceae such as Vibrio choleae.

1: Single Nucleotide Polymorphisms in Regulator-Encoding Genes Have an Additive Effect on Virulence Gene Expression in a Vibrio cholerae Clinical Isolate. Carignan BM, Brumfield KD, Son MS; mSphere. 2016; [Epub ahead of print] PMID:27668288