... andC-terminal helices of the c ring, respectively. The C-terminal helices show a clear handedness, and two of the rings face in the opposite direction in the membrane to the other two, forming the same patternas ... reconstituted c rings.(A, B) Crystalline assemblies of c rings. Although the number of subunits forming the rings can be seen, the signal-to-noise ratiomay be further enhanced by calculating their averages. ... transmembrane helix four as part of the ion-binding site. Therefore, the c ring of A. woodii hasonly 10 membrane-buried negative charges that areessential for binding the ion and also for the...