EPR Detection of an O_2 Surrogate Bound to Heme c_n of the Cytochrome b_6f Complex

摘要

The membrane-embedded cytochrome (cyt) b_6fomplex mediates electron transport between the photosystem II and photosystem I reaction center complexes in oxygenic photosynthesis. The 220 kDa b_6f complex consists of eight polypeptide subunits in each monomer of a functional dimer. Four relatively large subunits bind five redox cofactors of the complex (Fe_2S_2, hemes b_p, b_n, c_n, f). Cyt b_6f couples oxidation-reduction of lipophilic plastoquinol and reduction of high potential soluble plastocyanin or cyt c_6 to proton translocation across the membrane, thereby generating a transmembrane proton electrochemical potential gradient.