The large disc represents the oligomeric ring of FOc-subunits
embedded in the membrane (yellow); two hypothetic half-channels at the a- and c-subunits
interface are left white. Small circles on the disk are c-subunit
carboxyl groups (empty when deprotonated and negatively charged, gray
when protonated and neutral); gray circles are protons (higher
concentration below the membrane). When charged, carboxyls cannot enter
the membrane because of the energy penalty (red) and stay at the
protein-protein interface.
