Mr. Kaufman et al., BIOGENESIS AND REGULATION OF THE VIBRIO-CHOLERAE TOXIN-COREGULATED PILUS - ANALOGIES TO OTHER VIRULENCE FACTOR SECRETORY SYSTEMS, Gene, 126(1), 1993, pp. 43-49
Biogenesis of the toxin-coregulated pilus (TCP) of Vibrio cholerae 01
is essential for successful bacterial colonization of the small intest
ine. Pilus assembly requires the products of at least seven genes loca
ted on the chromosome adjacent to the pilin-encoding gene, tcpA. Previ
ously reported TnphoA insertions in the TCP-assembly-deficient V. chol
erae strains, KP2.21 and KP4.2, were isolated from the chromosome for
further analysis. Nucleotide sequencing of the tcpE=phoA and tcpF=phoA
fusions and corresponding clones of the region containing the intact
genes revealed the presence of two open reading frames (ORFs) of 340 a
nd 338 amino acids, designated TcpE and TcpF, respectively. The partia
l sequence of an ORF downstream from the TcpF coding sequence was dete
rmined to correspond to the global virulence regulator, ToxT. Proteins
corresponding to the observed ORFs were visualized with the T7 promot
er/RNA polymerase expression system. Computer-generated alignment algo
rithms predict that a homology exists between TcpE and the Klebsiella
pneumoniae pullulanase secretion proteins PulD and PulF, the Xanthomon
as campestris extracellular enzyme secretion factor XpsF, the Bacillus
subtilis DNA competence protein ComG-ORF2, and the Yersinia entercoli
tica Yop secretion determinant YscC. These observations provide a mode
l to investigate further the relationship between the secretion mechan
isms utilized by these seemingly diverse virulence determinants. Addit
ionally, an extreme C-terminal segment of TcpE shows striking homology
to the transmembrane segment of the eukaryotic integrin beta-1 chain,
which could imply a role for TcpE in not only TCP secretion, but also
host cell interaction.