FIG. 1.

Structures of pNIS-STX2 and pFIS-STX2. IS1203v of pNIS-STX2 has two ORFs (open arrows), designated ORFa and ORFb, and that of pFIS-STX2 has a single ORF, designated ORFa+b. ORFa+b is constructed by a 1-bp insertion in the region where ORFa and ORFb overlap, and this inserted nucleotide is indicated in bold type. The amino acid translations of the ORFs are shown within the open arrows. The open box and the thick arrow of pFIS-STX2 indicate IS1203v and the stx2 gene, respectively. The direction of the stx2 gene is the opposite of that of ORFa+b of IS1203v. stx2::IS1203v is numbered from the first nucleotide (position 1) to the last nucleotide (position 2555) of the complementary strand of the stx2 gene. IS1203v extends from position 263 to position 1573. The 25-bp long inverted repeats (IRs) are indicated at both ends of IS1203v. The 3-bp sequences (ATC) shown on both sides of IS1203v are direct repeats probably generated upon insertion of this IS element. ∗, the stop codon.