The three potential glycolipid binding sites of the Verotoxin 1 B subunit, their function in toxicity induction and cytokine release

grantor: University of Toronto'Esherichia coli'-elaborated Verotoxins (VT) consist of a single enzymatic A subunit and a pentamer of B subunits. The pentamer mediates toxin binding to the glycolipid globotriaosylceramide (Gb3). The aim of our studies was to determine the contribution of the three proposed Gb3 binding sites (known as sites 1, 2, and 3) of the B subunit to toxicity and cytokine induction. By mutating the three sites singly and in combination, we found that, in contrast to the site 3 mutant W34A, site 1 and site 2 mutants were significantly impaired in their ability to cause toxicity 'in vitro' and 'in vivo' as well as induce TNFÃ from human monocytes 'in vitro'. Our findings show the importance of Gb3 binding through sites 1 and 2 in mediating toxicity and cytokine induction as well as provide a correlation between the toxicity of the protein and its ability to induce cytokine release.M.Sc