Both AcfB and TcpI are transmembrane Neratinib manufacturer proteins, and the homology with MCPs has been noted previously (Everiss et al., 1994; Harkey et al., 1994). The tcpI and acfB genes were originally identified through TnphoA mutagenesis, and in this study a tcpI:TnphoA V. cholerae strain was found to exhibit wild-type levels of intestinal colonization, while an acfB∷TnphoA V. cholerae strain was approximately 10-fold defective for intestinal colonization (Peterson & Mekalanos, 1988). AcfB and TcpI share 26% amino acid identity over their entire

length, and the segments from aa 463 to 530 in AcfB and aa 453 to 520 in TcpI share 77% identity (Fig. 1 and Supporting Information, Fig. S1). Both proteins are predicted to have signal

peptides, and the N-terminal periplasmic portions contain a Cache motif (Anantharaman & Aravind, 2000), a signaling domain found in chemotaxis receptors. The transmembrane segments are predicted to be located at aa 278–292 in TcpI and aa 286–300 in AcfB (Cserzo et al., VE-821 molecular weight 1997), and the cytoplasmic portions contain a HAMP motif (Aravind & Ponting, 1999) and an MCP signaling domain (PF00015), both typically found in MCPs (Fig. 1). The Cache domain is predicted to be involved in small molecule recognition, while the HAMP domain has been shown to modulate conformation of MCP oligomers in response to ligand binding in the Cache domain and methylation of the MCP domain (Khursigara et al., 2008). To determine the roles of AcfB and TcpI in intestinal colonization, V. cholerae strains containing chromosomal mutations in acfB and tcpI were constructed. The tcpI gene is in a single gene operon, and so a deletion/insertion mutation (ΔtcpI∷Cm) was constructed; however, due to the location of acfB within a multigene operon, an in-frame deletion was constructed (ΔacfB) to prevent deleterious effects on downstream gene expression. We additionally constructed a V. cholerae strain with a

ΔcheY-3 mutation in this genetic background; cheY-3 is essential for V. cholerae chemotaxis (Butler & Camilli, 2004). The acfB, tcpI, and acfB tcpI V. cholerae strains were monitored for swimming behavior Cell press utilizing soft agar plates (Fig. 2). In this assay, the ΔcheY-3 mutant, despite being motile, demonstrates no net movement away from the point of inoculation, and productive movement could be complemented back to wild-type levels by providing cheY-3 in trans, as has been demonstrated previously (Butler & Camilli, 2004). The acfB and tcpI (single) mutants displayed motility patterns that were slightly greater than the wild-type strain, the acfB strain more so than the tcpI strain (Fig. 2); strains containing Tn-phoA fusion insertions in these genes were previously shown to similarly display enhanced motility patterns (Everiss et al., 1994; Harkey et al., 1994). In contrast, the acfB tcpI (double) mutant displayed a slightly smaller motility pattern than the wild-type strain.