Unusual organization associated to a tandem of IS231 may yield two peculiar cloverleaf secondary structures.
A 5.7-kb EcoRI fragment was cloned from plasmid DNA of Bacillus thuringiensis strain M15. It contains two insertion sequences (IS), IS231M2 and -M1 in the 5'-3' order, arranged in tandem, in same orientation, separated by a 540-bp region. The primary structure is typical of a composite transposon, here of 3847 bp in length, for which the name Tn231M is proposed. Each IS is delimited by 18-bp inverted repeats (IR), and flanked by 11-bp direct repeats (DR). Both IS share 99.3% nucleotide identities. IS231M1 has a single open reading frame (ORF) which encodes a putative 477-amino-acid transposase. IS231M2 has two smaller ORFs: ORF1 and ORF2, which could code for polypeptides of 329 and 118 amino acids in length, respectively. Further analysis reveals that the regions upstream of IS231M2, and downstream of -M1, and the 540-bp region, contain additional pairs of IR and DR. Interestingly, potential annealing between all pairs of IR and DR could generate two unusual cloverleaf secondary structures.
Xu
Dong
D
Agriculture and Agri-Food Canada, Research Centre, Québec, Canada.
Côté
Jean-Charles
JC
D001413:Bacillus thuringiensis / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D020080:Tandem Repeat Sequences
D004251:DNA Transposable Elements