Major component of the toxin co-regulated pilus (tcp) which is a type IV pilus essential for bacterial aggregation and subsequent colonization in the host small intestine. By ToxT that is required for tcpA transcriptional activation. Mechanistically, interacts directly with the tcpA promoter to mediate activation. The leader sequence region and some other sequence particularities suggest that TcpA may represent a novel class of pilin, and imply the existence of a novel signal peptidase. Deletion mutation abolishes Vibrio cholerae colonizing capacity (PubMed:2902187). It also shows loss of observable pili (PubMed:8594332).