title: Proteins released during high toxin production in Clostridium difficile.
abstract: The mechanism by which toxins A and B are released by Clostridium difficile is unknown and information about the other extracellular proteins of this bacterium is limited. The authors identified exported proteins from C. difficile strain VPI 10463 during conditions promoting high toxin production. Toxins A and B were released in a 1:1 ratio and the proportion of toxin in the extracellular fraction reached 50% during the stationary phase as compared to a proportion of <1% for typical cytoplasmic proteins, showing that toxin export was not due to bacterial lysis. A 47 kDa protein, released with similar kinetics to the toxins, was processed and showed weak similarity to the channel-forming protein TolC. Another protein released during high toxin production was unprocessed and showed similarity to XkdK encoded by the prophage PBSX in Bacillus subtilis, a protein supposedly exported via phage-specific holins. The two most abundant extracellular C. difficile proteins, found during both high and low toxin production, were processed and identified as shed S-layer proteins. As shown by N-terminal sequencing and PCR-based methods, there was a considerable sequence variation of the S-layer gene slpA in different serogroup reference strains. To conclude, C. difficile uses the classical Sec-dependent and probably also holin-like pathways to secrete a comparatively small repertoire of proteins.
authors.affiliation: AstraZeneca Research Center India, PO Box 359 Malleswaram, 560 003 Bangalore, India3.
authors.forename: Kakoli
authors.initials: K
authors.lastname: Mukherjee
authors.affiliation: Microbiology and Tumor Biology Center, Karolinska Institute, S-17177 Stockholm, Sweden2.|Department of Bacteriology, Swedish Institute for Infectious Disease Control, S-17182, Solna, Sweden1.
authors.forename: Sture
authors.initials: S
authors.lastname: Karlsson
authors.affiliation: Department of Bacteriology, Swedish Institute for Infectious Disease Control, S-17182, Solna, Sweden1.
authors.forename: Lars G
authors.initials: LG
authors.lastname: Burman
authors.affiliation: Department of Bacteriology, Swedish Institute for Infectious Disease Control, S-17182, Solna, Sweden1.
authors.forename: Thomas
authors.initials: T
authors.lastname: Åkerlund
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000096:biosynthesis*; D016360:Clostridioides difficile / Q000254:growth & development / Q000378:metabolism*; D017077:Culture Media, Conditioned; D004768:Enterotoxins / Q000096:biosynthesis*; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D017077:Culture Media, Conditioned; D004768:Enterotoxins; D008562:Membrane Glycoproteins; C055764:S-layer proteins; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile