title: Genetic rearrangements in the pathogenicity locus of Clostridium difficile strain 8864--implications for transcription, expression and enzymatic activity of toxins A and B.
abstract: The pathogenicity locus (PaLoc) of Clostridium difficile isolate 8864 was investigated to locate genetic rearrangements that would explain the exceptional pathogenicity of this particular isolate. Two major changes were defined: an insertion of 1.1 kb between the two genes tcdA and tcdE, coding for the enterotoxin and an accessory protein of unknown function, respectively, and a deletion of 5.9 kb encompassing the 3' ends of tcdA and tcdC. Transcription of the tcdA-E genes is severely affected by both rearrangements, explaining the demonstrated complete lack of TcdA polypeptide. We present a model of coordinate, growth-related transcription of the tcdA-E genes that confirms our previous findings in strain 10463. Recombinant TcdA-8864 had UDP-glucose-glucosyltransferase activity, proving that the N-terminal 698 amino acids of the polypeptide represent the catalytic domain. However, this truncated TcdA molecule lacks a ligand and translocation domain. To assess the catalytic domain of TcdB-8864, the sequence of the 5' end of its gene was determined. TcdB-8864 shows high homology to TcdB-1470 but lower homology to TcdB-10463 within this domain. This fits well with the altered glucosylation specificity of TcdB-8864 (Rac1, Rap2 and Ra1). Having defined the variations of transcription, expression and enzymatic activity of toxins A and B, implications for the pathogenic potential of strain 8864 are discussed.
authors.affiliation: Verfügungsgebäude für Forschung und Entwicklung, Institut für Medizinische Mikrobiologie und Hygiene, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Soehn
authors.forename: A
authors.initials: A
authors.lastname: Wagenknecht-Wiesner
authors.forename: P
authors.initials: P
authors.lastname: Leukel
authors.forename: M
authors.initials: M
authors.lastname: Kohl
authors.forename: M
authors.initials: M
authors.lastname: Weidmann
authors.forename: C
authors.initials: C
authors.lastname: von Eichel-Streiber
authors.forename: V
authors.initials: V
authors.lastname: Braun
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001427:Bacterial Toxins / Q000737:chemistry*; D016360:Clostridioides difficile / Q000235:genetics / Q000472:pathogenicity*; D019204:GTP-Binding Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D005964:Glucosyltransferases / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D006031:Glycosylation; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D011994:Recombinant Proteins; D005964:Glucosyltransferases; D006026:Glycoside Hydrolases; D019204:GTP-Binding Proteins