NMR studies on the dynamics and structure of Verotoxin-1 B subunits binding to its functional plasma membrane receptor, Globotriaosylceramide, Gb3

Introduction Verotoxin (VT) was first reported by Konowalchuk et al. in 1977. Although VT-producing E. coli strains belong to several different serotypes, 0157:H7 is the dominant serotype isolated from patients suffering from food poisoning. The infection frequently develops into hemorrhagic colitis. Furthermore, about 10% of these cases develop into the haemolytic uremic syndrome, which is the leading cause of acute renal failure in children. Verotoxins belong to the AB5 class of bacterial toxins. The enzymatic A-subunit inhibits protein synthesis in the cell, by selectively attacking the ribosome by removing the adenine residue at position 4324 of the 28S subunit. However, the A-subunit requires the presence of the homopentameric B-sub-units to achieve toxicity. The role of the B-subunits is attachment to the target cells and the translocation of the A-subunit into the cytoplasm. The functional receptor of verotoxin is the glycolipid globotriaosylceramide [Gb3, Galα1-4Galβ1-4Glcceramide]. The binding affinity of VTB to Gb3 is in the millimolar range (Kd = 1 x 10 -3 ). Since binding to the cell surface has been shown to be a crucial step in the cytotoxicity of verotoxin, designing inhibitors to block toxin binding would be an effective approach to therapy development.