Fig. 3.

Atomic model of the epsilon toxin (Etx) pore. Cartoon representation of the heptameric Etx model with height, width and lumen dimensions indicated (a, b). The monomers are coloured by domain: green—receptor-binding domain (RBD); blue—β-hairpin domain; yellow—cap domain. c Close-up view of the inner β-barrel and membrane-spanning region. Residues identified in previous studies as important to receptor binding in the RBD, as well as residues forming the aromatic belts, are highlighted in stick representation. The approximate boundaries of the lipid bilayer are coloured light brown. d Close-up view of the double β-barrel (DBB) fold viewed from the membrane side with interacting residues shown in stick representation