title: Cloning and sequencing of a Shiga-like toxin type II variant from Escherichia coli strain responsible for edema disease of swine.
abstract: A Shiga-like toxin type II variant (SLT-IIv) is produced by strains of Escherichia coli responsible for edema disease of swine and is antigenically related to Shiga-like toxin type II (SLT-II) of enterohemorrhagic E. coli. However, SLT-IIv is only active against Vero cells, whereas SLT-II is active against both Vero and HeLa cells. The structural genes for SLT-IIv were cloned from E. coli S1191, and the nucleotide sequence was determined and compared with those of other members of the Shiga toxin family. The A subunit genes for SLT-IIv and SLT-II were highly homologous (94%), whereas the B subunit genes were less homologous (79%). The SLT-IIv genes were more distantly related (55 to 60% overall homology) to the genes for Shiga toxin of Shigella dysenteriae type 1 and the nearly identical Shiga-like toxin type I (SLT-I) of enterohemorrhagic E. coli. (These toxins are referred to together as Shiga toxin/SLT-I.) The A subunit of SLT-IIv, like those of other members of this toxin family, had regions of homology with the plant lectin ricin. SLT-IIv did not bind to galactose-alpha 1-4-galactose conjugated to bovine serum albumin, which is an analog of the eucaryotic cell receptor for Shiga toxin/SLT-I and SLT-II. These findings support the hypothesis that SLT-IIv binds to a different cellular receptor than do other members of the Shiga toxin family but has a similar mode of intracellular action. The organization of the SLT-IIv operon was similar to that of other members of the Shiga toxin family. Iron did not suppress SLT-IIv or SLT-II production, in contrast with its effect on Shiga toxin/SLT-I. Therefore, the regulation of synthesis of SLT-IIv and SLT-II differs from that of Shiga toxin/SLT-I.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003603:Cytotoxins / Q000235:genetics*; D004487:Edema / Q000382:microbiology / Q000662:veterinary; D004926:Escherichia coli / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary; D005796:Genes; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D012276:Ricin / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D022622:Shiga Toxin 1; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology; D014709:Vero Cells
chemical_list: D001427:Bacterial Toxins; D003603:Cytotoxins; D022622:Shiga Toxin 1; D012276:Ricin