FIGURE 7.

PFO^β4β5 forms SDS-sensitive oligomers on membranes. A and B, EMs of membrane-bound PFO^β4β5 in its oxidized state (A) and reduced (pore-forming) state (B). Scale bars, 50 Å. The intermolecular interaction of monomers was determined by FRET between donor- and acceptor-labeled PFO^β4β5. C, FRET-dependent donor quenching measured in its oxidized membrane-bound form. Compare the DA and DU samples. After PFO^β4β5 had been allowed to interact and donor quenching was at its maximum we added unlabeled PFO^PPL (dashed line) to determine whether the interaction of the PFO^β4β5 was reversible, like that observed for PFO^W165T (Fig. 5B).