Cytochrome b6-f complex (Cytochrome b6f complex)

The **cytochrome b6-f complex** is a multi-subunit, transmembrane protein complex central to the electron transport chain in oxygenic photosynthesis, found in the thylakoid membranes of plants, algae, and cyanobacteria[1][2][4][6]. It functions as the key intermediary, mediating electron transfer from plastoquinol (PQH2) to plastocyanin (PC) or cytochrome c6, effectively bridging **photosystem II (PSII)** and **photosystem I (PSI)**[4][8]. The complex is a symmetric dimer (~220 kDa), typically composed of eight different subunits, including cytochrome f, cytochrome b6, subunit IV, the Rieske iron-sulfur protein, and several small membrane proteins[3][7][8]. It contains multiple redox-active cofactors: four hemes, a [2Fe-2S] cluster, chlorophyll a, and β-carotene[1][4][3].\n\nFunctionally, the cytochrome b6-f complex plays an essential role in generating a proton gradient across the thylakoid membrane, driving ATP synthesis and regulating distribution of excitation energy between the two photosystems[1][2]. It participates in both linear and cyclic electron transfer, impacting photosynthetic efficiency and ATP/NADPH balance[2][4][6]. Research often uses quinone analog inhibitors to probe its function, but there are no clinically approved drugs targeting this complex, as it is unique to photosynthetic organisms and absent in humans.\n\nThere is no evidence or clinical context for this complex in human disease, drug interaction, or relevant safety/biomarker concerns. It is a model target in plant biology and bioenergetics, not pharmacology.

Other names

cytochrome b6fcyt b6fb6f complexcytochrome b6/f complex

N/A (no approved drugs; inhibition in research via quinone analogs that block electron transfer)