Identification of a cytochrome bc1-aa3 supercomplex in Rhodobacter sphaeroides

Biochim Biophys Acta Bioenerg. 2021 Aug 1;1862(8):148433. doi: 10.1016/j.bbabio.2021.148433. Epub 2021 Apr 29.


Respiration is carried out by a series of membrane-bound complexes in the inner mitochondrial membrane or in the cytoplasmic membrane of bacteria. Increasing evidence shows that these complexes organize into larger supercomplexes. In this work, we identified a supercomplex composed of cytochrome (cyt.) bc1 and aa3-type cyt. c oxidase in Rhodobacter sphaeroides. We purified the supercomplex using a His-tag on either of these complexes. The results from activity assays, native and denaturing PAGE, size exclusion chromatography, electron microscopy, optical absorption spectroscopy and kinetic studies on the purified samples support the formation and coupled quinol oxidation:O2 reduction activity of the cyt. bc1-aa3 supercomplex. The potential role of the membrane-anchored cyt. cy as a component in supercomplexes was also investigated.

Keywords: Bioenergetics; Cytochrome bc(1) complex; Electron transfer; Respiratory supercomplex; aa(3)-type cytochrome c oxidase; flow-flash.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Membrane / metabolism*
  • Electron Transport
  • Electron Transport Complex III / chemistry
  • Electron Transport Complex III / metabolism*
  • Electron Transport Complex IV / chemistry
  • Electron Transport Complex IV / metabolism*
  • Hydroquinones / metabolism*
  • Kinetics
  • Oxidation-Reduction
  • Rhodobacter sphaeroides / enzymology*


  • Hydroquinones
  • Electron Transport Complex IV
  • Electron Transport Complex III