title: Vibrio cholerae Hcp, a secreted protein coregulated with HlyA.
abstract: Hcp is a 28-kDa secreted protein of Vibrio cholerae regulated coordinately with the hemolysin, HlyA. Both proteins show a dependence on HlyU for expression, suggesting that Hcp may be secreted by V. cholerae in vivo. We have identified and sequenced two genes for Hcp, designated hcpA and hcpB (hemolysin-coregulated protein). The genes encode identical amino acid sequences. Both express a 28-kDa protein, despite open reading frames with only a 19-kDa capacity, suggesting that the Hcp protein runs aberrantly on polyacrylamide gel electrophoresis. There is no cleavage involved in secretion of Hcp from the cell, suggesting a novel mechanism of secretion. An hcp null mutant was constructed, and this strain displayed no deficiency in virulence or colonization in the infant mouse cholera model. From sequence data and primer extension analysis, we predict that the hcp promoter is the sigma 54 type, with a candidate integration host factor binding site upstream. Although hcp and hlyA are coregulated by HlyU, there are no obvious similarities between their promoters. We predict that an intermediate regulator may be involved in the activation of hcp by HlyU. This raises the possibility that HlyU is part of a regulatory cascade.
authors.affiliation: Department of Microbiology and Immunology, University of Adelaide, Australia.
authors.forename: S G
authors.initials: SG
authors.lastname: Williams
authors.forename: L T
authors.initials: LT
authors.lastname: Varcoe
authors.forename: S R
authors.initials: SR
authors.lastname: Attridge
authors.forename: P A
authors.initials: PA
authors.lastname: Manning
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D015153:Blotting, Western; D002771:Cholera / Q000382:microbiology; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014734:Vibrio cholerae / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C097322:Hcp protein, Vibrio cholerae; D006460:Hemolysin Proteins; D012333:RNA, Messenger; C084287:hlyA protein, Vibrio cholerae