PNNL

Abstract

The cyt bc1 complex and the related cyt b6f and bc-type complexes are key components of chemiosmotic energy conversion in mitochondria, chloroplasts and many bacteria. These complexes oxidize a range of different quinol or hydroquinone (QH2) molecules—ubihydroquinone (UQH2) in the case of mitochondria and many bacteria, plastohydroquinone (PQH2) in chloroplasts and cyanobacteria, and menahydroquinone in many bacteria—to the corresponding quinone (Q), and reduce a range of soluble electron carriers, e.g. cyt c in purple bacteria and mitochondria, plastocyanin in chloroplasts. The redox reactions are coupled to the translocation of protons across the energetic membrane to store energy in an electrochemical proton gradient, or proton motive force (pmf) which drives ATP synthesis.