title: A nonsense mutation abrogates production of a functional enterotoxin A in Clostridium difficile toxinotype VIII strains of serogroups F and X.
abstract: Clostridium difficile strains of toxinotype VIII from serogroups F and X are described as toxin B-positive, toxin A-negative (TcdB+ A-), although they harbour almost the entire tcdA gene. To identify the reason for the lack of TcdA detection, we analyzed catalytic and ligand domains of TcdA-1470 of the type strain of serogroup F, strain 1470. Using recombinant fragments, the C-terminal immunodominant ligand domain TcdA3-1470, spanning amino acid residues 1694-2711 (corresponding to VPI 10463 sequence), was detected in Western blots. Similar experiments using the recombinant N-terminal catalytic fragment TcdAc1-2-1470 (amino acid positions 1-544) failed. In addition, this fragment showed no glucosylation activity. We determined the size and the position of alterations in the ligand domain tcdA3-1470 by DNA sequencing. Within the N-terminal fragment tcdAc1-2-1470, a nonsense mutation was identified introducing a stop codon at amino acid position 47. Identical mutations were found in the two serogroup X strains 17663 and 10355. The mutation might explain the lack of TcdA production observed in strains of serotypes F and X.
authors.affiliation: Institut für Medizinische Mikrobiologie und Hygiene, Johannes Gutenberg-University, Mainz, Germany. veichel@mail.uni-mainz.de
authors.forename: C
authors.initials: C
authors.lastname: von Eichel-Streiber
authors.forename: I
authors.initials: I
authors.lastname: Zec-Pirnat
authors.forename: M
authors.initials: M
authors.lastname: Grabnar
authors.forename: M
authors.initials: M
authors.lastname: Rupnik
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis; D015153:Blotting, Western; D020134:Catalytic Domain / Q000235:genetics*; D016360:Clostridioides difficile / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D004768:Enterotoxins / Q000096:biosynthesis / Q000235:genetics*; D017353:Gene Deletion; D005798:Genes, Bacterial; D006801:Humans; D020125:Mutation, Missense; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis
chemical_list: D001426:Bacterial Proteins; D004768:Enterotoxins; D010446:Peptide Fragments; D011994:Recombinant Proteins