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A chimeric ribozyme in Clostridium difficile combines features of group I introns and insertion elements
Author(s) -
Braun Veit,
Mehlig Markus,
Moos Michael,
Rupnik Maja,
Kalt Bettina,
Mahony David E.,
Von EichelStreiber Christoph
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01965.x
Subject(s) - group ii intron , biology , insertion sequence , group i catalytic intron , ribozyme , genetics , intron , gene , open reading frame , rna splicing , orfs , operon , rna , transposable element , escherichia coli , genome , peptide sequence
Cd ISt1 , a DNA insertion of 1975 bp, was identified within tcdA‐C34, the enterotoxin gene of the Clostridium difficile isolate C34. Located in the catalytic domain A1‐C34, Cd ISt 1 combines features of two genetic elements. Within the first 434 nt structures characteristic for group I introns were found; encoding the two transposase‐like proteins tlpA and tlpB nucleotides 435–1975 represent the remainder of a IS 605 ‐like insertion element. We show that the entire Cd ISt1 is accurately spliced from tcdA‐C34 primary transcripts and that purified TcdA‐C34 toxin is of regular size and catalytic activity. A search for Cd ISt1‐ related sequences demonstrates that the element is widespread in toxinogenic and non‐toxinogenic C. difficile strains, indicating the mobility of Cd ISt1 . In strain C34, we characterize 10 Cd ISt1 variants; all are highly homologous to Cd ISt1 (> 93% identity), integrated in bacterial open reading frames (ORFs), show the typical composite structure of Cd ISt1 and are precisely spliced from their primary transcripts. Cd ISt1 ‐like chimeric ribozymes appear to combine the invasiveness of an insertion element with the splicing ability of a group I intron, rendering transposition harmless for the interrupted gene.