Fig. 4.

Conformational changes accompanying pore formation. Wire representation of epsilon toxin (Etx) monomers in the water-soluble and membrane-inserted state coloured by domain as in Fig. 3 and viewed from different angles (a–c). The two models were superimposed by their receptor-binding domain (RBD), which remains mostly unchanged during the transition. The cap domain collapses by 45 Å allowing the pre-insertion strands to get closer to the membrane and form the inner β-barrel. The heptameric pore is also shown for context. Curved arrow in c illustrates outward movement of the cap domain in the membrane-inserted form