GENETIC ORGANIZATION AND SEQUENCE OF THE PROMOTER-DISTAL REGION OF THE TCP GENE-CLUSTER OF VIBRIO-CHOLERAE

The nucleotide sequence of the promoter distal region of the major ope ron associated with biosynthesis of TCP, the toxin coregulated pilus o f Vibrio cholerae has been determined. The genes tcpR, tcpD, tcpS, tcp T, tcpE and tcpF are organized to permit translational coupling and ar e followed by an inverted repeat structure which is likely to act as a strong Rho-independent terminator. TcpS and TcpF possess N-terminal s ignal sequences and would be expected to be periplasm and outer membra ne located, respectively. TcpT and, to a lesser extent, TcpE show homo logy to protein transport and secretion proteins identified in a numbe r of other bacteria. TcpR and TcpD are also predicted to be localized in the membrane based on their hydrophobicity profiles. In the case of TcpD, this may be in the outer membrane, as the N terminus is reminis cent of the TcpA signal sequence processed by TcpJ. Taken together wit h other data on the tcp region, it is clear that the types of proteins involved in the biogenesis of TCP are, at least in some cases, relate d to those associated with type-4 pilus biosynthesis but differ marked ly from those for other well-described fimbrial systems, such as Type 1, K88, K99 or Pap pili. The complete sequence data for TCP biosynthes is-controlling genes are now available and represent the only complete example of a type-4 pilus-like system.