The Shiga and Shiga-Like Cytotoxins: Gene Regulation and Functional Analysis of the Binding Subunits

Abstract : Strains of Escherichia coli produce cytotoxins which are related to the Shiga toxin produced by Shigella dysenteriae type 1. Shiga-like toxin type I (SLT-I) and Shiga-like toxin type II (SLT-II) are produced by enterohemorrhagic E. coli which cause hemorrhagic colitis and/or the hemolytic uremic syndrome in humans . Shiga toxin, SLT-I, and SLT-II are primarily cell-associated cytotoxins that kill both Vero cells and HeLa cells in culture. A third SLT, the Shiga-like toxin type II variant (SLT-IIv), is produced by strains of E. coli responsible for the edema disease of swine. SLT-IIv, which is antigenically related to SLT-II, is markedly more cytotoxic for Vero than HeLa cells. structurally, all of these toxins are comprised of an A subunit, which is responsible for the enzymatic activity, and multiple B subunits which bind the toxin to a eucaryotic cell receptor.