title: Identification and molecular analysis of the gene encoding Rickettsia typhi hemolysin.
abstract: Rickettsia typhi, the causative agent of murine typhus, grows directly within the host cell cytoplasm, accumulating a large number of progeny, and eventually lyses the cells. Typhus group rickettsiae (R. typhi and R. prowazekii) adhere to and lyse human and sheep erythrocytes. However, the molecular mechanism underlying erythrocyte lysis by R. typhi has not been defined. Here we describe the cloning and nucleotide sequence analysis of the gene (tlyC) encoding a hemolysin from R. typhi. DNA sequence analysis of R. typhi tlyC revealed an open reading frame of 912 bp, which encodes a protein of 304 amino acids with a predicted molecular mass of 38 kDa. To associate the R. typhi tlyC gene product with hemolytic activity, we performed complementation studies with hemolysin-negative Proteus mirabilis WPM111 (a HpmA(-) mutant of BA6163) transformed with R. typhi tlyC or R. typhi GFPuv-tlyC constructs. We demonstrated that the cloned tlyC gene conferred a hemolytic phenotype on an otherwise nonhemolytic mutant of P. mirabilis. The availability of the cloned R. typhi tlyC will permit further characterization and definition of its role in rickettsial virulence.
authors.affiliation: Department of Microbiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA. sradu001@maryland.edu
authors.forename: S
authors.initials: S
authors.lastname: Radulovic
authors.forename: J M
authors.initials: JM
authors.lastname: Troyer
authors.forename: M S
authors.initials: MS
authors.lastname: Beier
authors.forename: A O
authors.initials: AO
authors.lastname: Lau
authors.forename: A F
authors.initials: AF
authors.lastname: Azad
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000235:genetics* / Q000633:toxicity; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012286:Rickettsia typhi / Q000235:genetics*; D012756:Sheep; D014169:Transformation, Bacterial; D014709:Vero Cells
chemical_list: D001426:Bacterial Proteins; D006460:Hemolysin Proteins; C090674:TlyC protein, Brachyspira hyodysenteriae