Figure 1: The cytochrome b6f dimer operates through a modified Q-cycle.
Left, box schematic; the b6f complex transfers two protons (green arrows) per electron transferred (blue arrows) along high (Fe2S2 cluster, cytochrome f) and low potential chains (bl, bh, ci haems). Quinol (QH2) oxidation at Qo site, Quinone (Q) reduction at Qi site. Right, structure (redrawn from ref. 35) depicting haems b (purple), ci and f (red), Fe2S2 cluster (yellow and orange ball-and-stick model), cytochrome b6 (cyan), subunit IV (blue), Rieske subunit (yellow), cytochrome f (red), PetG, L, M and N subunits (green). Magnification of Qi site comprising bh and ci haems.
