title: An electronic bus bar lies in the core of cytochrome bc1.
abstract: The ubiquinol-cytochrome c oxidoreductases, central to cellular respiration and photosynthesis, are homodimers. High symmetry has frustrated resolution of whether cross-dimer interactions are functionally important. This has resulted in a proliferation of contradictory models. Here, we duplicated and fused cytochrome b subunits, and then broke symmetry by introducing independent mutations into each monomer. Electrons moved freely within and between monomers, crossing an electron-transfer bridge between two hemes in the core of the dimer. This revealed an H-shaped electron-transfer system that distributes electrons between four quinone oxidation-reduction terminals at the corners of the dimer within the millisecond time scale of enzymatic turnover. Free and unregulated distribution of electrons acts like a molecular-scale bus bar, a design often exploited in electronics.
authors.affiliation: Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Swierczek
authors.forename: Ewelina
authors.initials: E
authors.lastname: Cieluch
authors.forename: Marcin
authors.initials: M
authors.lastname: Sarewicz
authors.forename: Arkadiusz
authors.initials: A
authors.lastname: Borek
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Moser
authors.forename: P Leslie
authors.initials: PL
authors.lastname: Dutton
authors.forename: Artur
authors.initials: A
authors.lastname: Osyczka
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004583:Electrons; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D017354:Point Mutation; D011487:Protein Conformation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000201:enzymology*; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D050505:Mutant Proteins; D021122:Protein Subunits; D014451:Ubiquinone; D045304:Cytochromes c; D014450:Electron Transport Complex III; C003741:ubiquinol