The Vibrio cholerae toxin-coregulated-pilus gene tcpI encodes a homolog of methyl-accepting chemotaxis proteins.
Virulence gene activation in Vibrio cholerae is under the control of the ToxR-ToxT regulatory cascade. The ToxR regulon consists of genes required for toxin-coregulated-pilus (TCP) biogenesis, accessory colonization factor genes, cholera toxin genes, and ToxR-activated genes (tag) of unknown function. The tagB gene was isolated by using a tagB::TnphoA fusion junction to probe a V. cholerae )395 bacteriophage lambda library. Nucleotide sequence analysis revealed that tagB is identical to tcpI, a gene which encodes a protein that negatively regulates the synthesis of the major pilin subunit of TCP (TcpA). Our results show that the tcpI gene encodes a 620-amino-acid protein that shares extensive sequence similarity with the highly conserved signaling domain in methyl-accepting chemotaxis proteins. Expression of tcpI in Escherichia coli results in the synthesis of a 71-kDa polypeptide that becomes localized to the inner membrane. Similarly, TcpI-PhoA alkaline phosphatase activity is enriched in V. cholerae inner membrane preparations. Colonies of V. cholerae tcpI::TnphoA mutant cells display increased swarming on solid media when compared with those of the parental V. cholerae O395. Taken together, these observations suggest that TcpI may play a dual role in promoting vibrio colonization of the small bowel. In response to the appropriate environmental signal(s), TcpI permits maximum expression of tcpA while simultaneously reducing vibrio chemotaxis-directed motility. We believe coordinate regulation of colonization and motility determinants, in such a fashion, facilitates efficient V. cholerae microcolony formation.
Harkey
C W
CW
Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130.
Everiss
K D
KD
Peterson
K M
KM
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis; D001426:Bacterial Proteins / Q000096:biosynthesis; D001483:Base Sequence; D002451:Cell Compartmentation; D002465:Cell Movement / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D036781:Fimbriae Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D005809:Genes, Regulator / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D000072236:Methyl-Accepting Chemotaxis Proteins; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011487:Protein Conformation; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015533:Transcriptional Activation; D014734:Vibrio cholerae / Q000235:genetics*
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; C085807:TcpA protein, Vibrio cholerae; D036781:Fimbriae Proteins