Cloning and nucleotide sequencing of Vero toxin 2 variant genes from Escherichia coli O91:H21 isolated from a patient with the hemolytic uremic syndrome.
Cellular DNA extracted from Escherichia coli strain B2F1 (O91:H21) was found to contain two separate DNA sequences that hybridized with a Vero toxin 2 (VT2)-specific gene probe under stringent conditions. These two sequences were cloned and both were shown to encode a variant of Vero toxin 2 (VT2vh). The nucleotide sequences of the operons encoding VT2vh, designated as vtx2ha and vtx2hb, were determined. The two operons were nearly identical (99% overall DNA homology) and both encoded A subunits of 319 amino acid residues and B subunits of 89 amino acid residues, the A and B subunit genes being separated by a stretch of 14 bp. The A and B subunit genes of the vtx2ha operon exhibited 98.6% and 95.5% DNA homology, respectively, with those of the slt-II operon encoding Shiga-like toxin II (or VT2) cloned from a strain from a patient with hemorrhagic colitis, while the A and B subunit genes of the vtx2ha operon showed 94.5% and 82.8% DNA homology, respectively, with those of the slt-IIv operon encoding a SLT-II variant cloned from a strain isolated from a pig with edema disease. The nucleotide sequences of the presumed promoters and presumptive ribosome binding sites in the vtx2ha, vtx2hb, and slt-II, and slt-IIv operons were identical. These results indicate that nucleotide sequences encoding a family of VT2-related toxins are present in various strains of E. coli and that the sequences of the genes for A subunits are better conserved than those of the B subunit genes.
Department of Microbiology, Faculty of Medicine, Kyoto University, Japan.
H
H
Ito
A
A
Terai
H
H
Kurazono
Y
Y
Takeda
M
M
Nishibuchi
D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000302:isolation & purification; D005798:Genes, Bacterial; D006463:Hemolytic-Uremic Syndrome / Q000382:microbiology*; D006801:Humans; D008969:Molecular Sequence Data; D009876:Operon; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2
D001427:Bacterial Toxins; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2