InterPro domain: IPR005870

This entry describes subunit IV of the cytochrome b6/f complex. The cyt b6/f complex is central to the functions of oxygenic photosynthetic electron transport in cyanobacteria and its equivalents in algae and higher plants, mediating electron transfer between photosystem II (PSII) and photosystem I (PSI) reaction centre complexes. The cyt b6f complex consists of a cytochrome b core, in addition to cytochrome f, Rieske 2Fe-2S, and subunits IV, V, VI, VII. The complex has a central quinone exchange cavity, which is defined by two monomers that resemble the respiratory cytochrome bc1 complex [ 1 ]. Cyt b6f has three prosthetic groups not found in cytbc1: chlorophyll-a, beta-carotene and a structurally unique covalently bound haem. The haem is thought to function in cyclic electron transport via anionic ferredoxin. Each monomer of the complex contains a molecule of chlorophyll-a and beta-carotene. Subunit IV is one of the principal subunits for the binding of the redox prosthetic groups.

1. Transmembrane traffic in the cytochrome b6f complex. Annu. Rev. Biochem. 75, 769-90