Figure 2. Structure of dimeric b₆f complex from M.laminosus (PDB ID 2E74).

(240,000 MW; per monomer, 8 subunits/7 prosthetic groups; 8 lipids) Subunit organization and lipid binding sites. (A) View along membrane plane showing the positions of the 8 subunits. Color code: cytochrome f (pet A), yellow; cytochrome b₆ (pet B), cyan); Rieske [2Fe-2S] protein (Pet C), orange; subunit IV/Pet D (pink), Pet G (teal), Pet L (light brown), Pet M (green) and Pet N (gray). (B) Side view of M. laminosus b₆f complex showing bound lipids, detergents and pigments. (C) Polytopic core of the b₆f complex. Cyt b₆ (4 TMH, cyan) and subunit IV (3 TMH, pink) form the core of the b₆f monomer. The cytb₆TMH form a four helix bundle. SubIV is organized around the bundle as a bipartite structure, with the E-helix separated from the F and G TMH. (D) Peripheral four helix bundle formed by the small Pet subunits, Pet G, L, M and N. In addition, including ferredoxin-NADP⁺-reductase (FNR), which may mediate electron transfer from PSI to cyt b₆f. (Fig. 1) In addition, there are four soluble subunits that associate with purified b₆f complex from plant or algal sources, but have not been seen in the crystal structures and have presumably dissociated and been lost during crystallization: the Pet P polypeptide seen in cyanobacteria, the light-harvesting LHCII chlorophyll protein kinase Stt7-STN7, the correlated phosphatase, and the PetO nuclear-encoded phosphorylatable subunit,.