title: Characterization of a pore-forming cytotoxin expressed by Salmonella enterica serovars typhi and paratyphi A.
abstract: Cytolysin A (ClyA) is a pore-forming cytotoxic protein encoded by the clyA gene that has been characterized so far only in Escherichia coli. Using DNA sequence analysis and PCR, we established that clyA is conserved in the human-specific typhoid Salmonella enterica serovars Typhi and Paratyphi A and that the entire clyA gene locus is absent in many other S. enterica serovars, including Typhimurium. The gene products, designated ClyA(STy) and ClyA(SPa), show >/=90% amino acid identity to E. coli cytolysin A, ClyA(EC), and they are immunogenically related. The Salmonella proteins showed a pore-forming activity and are hence functional homologues to ClyA(EC). The chromosomal clyA(STy) gene locus was expressed at detectable levels in the serovar Typhi strains S2369/96 and S1112/97. Furthermore, in the serovar Typhi vaccine strain Ty21a, expression of clyA(STy) reached phenotypic levels, as detected on blood agar plates. The hemolytic phenotype was abolished by the introduction of an in-frame deletion in the clyA(STy) chromosomal locus of Ty21a. Transcomplementation of the mutant with a cloned clyA(STy) gene restored the hemolytic phenotype. To our knowledge, Ty21a is the first reported phenotypically hemolytic Salmonella strain in which the genetic determinant has been identified.
authors.affiliation: Department of Molecular Biology, Umeå University, S-90187 Umeå Swedish Institute for Infectious Disease Control, S-17182 Solna, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Oscarsson
authors.forename: Marie
authors.initials: M
authors.lastname: Westermark
authors.forename: Sven
authors.initials: S
authors.lastname: Löfdahl
authors.forename: Björn
authors.initials: B
authors.lastname: Olsen
authors.forename: Helena
authors.initials: H
authors.lastname: Palmgren
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Mizunoe
authors.forename: Sun Nyunt
authors.initials: SN
authors.lastname: Wai
authors.forename: Bernt Eric
authors.initials: BE
authors.lastname: Uhlin
mesh_terms: D001483:Base Sequence; D003603:Cytotoxins / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D015870:Gene Expression; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010641:Phenotype; D012482:Salmonella paratyphi A / Q000235:genetics* / Q000472:pathogenicity; D012485:Salmonella typhi / Q000235:genetics* / Q000472:pathogenicity; D012689:Sequence Homology, Nucleic Acid
chemical_list: D003603:Cytotoxins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C119944:hlyE protein, E coli