Shiga-like toxins (SLTs), are also called Verotoxins. Enterohemorrhagic Escherichia coli (EHEC) strains which are primarily of serotypes 0157:H7, 026:H11, and O111:H8 have been incriminated as etiologic agents of hemorrhagic colitis and Hemolytic-uremic syndrome, a generalized disease characterized by acute renal failure, thrombocytopenia, and microangiopathic hemolytic anemia. There are several distinct E.coli SLTs. SLT-I and SLT-II are produced by EHEC.
SLT-I and Shiga toxin share >99% deduced amino acid sequence homology, whereas SLT-I and SLT-II share about 60% deduced amino acid sequence homology. SLT-I and SLT-II are antigenically distinct. Antibodies to SLT-II can also neutralize a variant of SLT-II (designated SLT-Iiv) produced by strains of E.coli that cause edema. SLT-IIv is cytotoxic for Vero but not HeLa cells, distinguishing it from SLT-II.
The protein structure of the toxin consists of two domains: the A polypeptide that inhibits protein synthesis by targeting ribosomes, and the B polypeptide pentamer that binds to the eukaryotic cell receptor globotriaosylceramide (Gb3) leading to receptor-mediated endocytosis.