title: Regulatory role of the respiratory supercomplex factors in Saccharomyces cerevisiae.
abstract: The respiratory supercomplex factors (Rcf) 1 and 2 mediate supramolecular interactions between mitochondrial complexes III (ubiquinol-cytochrome c reductase; cyt. bc1) and IV (cytochrome c oxidase; CytcO). In addition, removal of these polypeptides results in decreased activity of CytcO, but not of cyt. bc1 In the present study, we have investigated the kinetics of ligand binding, the single-turnover reaction of CytcO with O2, and the linked cyt. bc1-CytcO quinol oxidation-oxygen-reduction activities in mitochondria in which Rcf1 or Rcf2 were removed genetically (strains rcf1Δ and rcf2Δ, respectively). The data show that in the rcf1Δ and rcf2Δ strains, in a significant fraction of the population, ligand binding occurs over a time scale that is ∼100-fold faster (τ ≅ 100 μs) than observed with the wild-type mitochondria (τ ≅ 10 ms), indicating structural changes. This effect is specific to removal of Rcf and not dissociation of the cyt. bc1-CytcO supercomplex. Furthermore, in the rcf1Δ and rcf2Δ strains, the single-turnover reaction of CytcO with O2 was incomplete. This observation indicates that the lower activity of CytcO is caused by a fraction of inactive CytcO rather than decreased CytcO activity of the entire population. Furthermore, the data suggest that the Rcf1 polypeptide mediates formation of an electron-transfer bridge from cyt. bc1 to CytcO via a tightly bound cyt. c We discuss the significance of the proposed regulatory mechanism of Rcf1 and Rcf2 in the context of supramolecular interactions between cyt. bc1 and CytcO.
authors.affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden;
authors.forename: Camilla
authors.initials: C
authors.lastname: Rydström Lundin
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland.
authors.forename: Christoph
authors.identifier: 0000-0002-4642-6088
authors.initials: C
authors.lastname: von Ballmoos
authors.affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden;
authors.forename: Martin
authors.initials: M
authors.lastname: Ott
authors.affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden;
authors.forename: Pia
authors.initials: P
authors.lastname: Ädelroth
authors.affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden; peterb@dbb.su.se.
authors.forename: Peter
authors.initials: P
authors.lastname: Brzezinski
mesh_terms: D004579:Electron Transport / Q000235:genetics; D014450:Electron Transport Complex III / Q000235:genetics / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: C573148:Rcf1 protein, S cerevisiae; C573149:Rcf2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV; D014450:Electron Transport Complex III
keywords: cytochrome aa3; cytochrome bc1; cytochrome c oxidase; electron transfer; membrane protein