title: Ubiquinone is not required for proton conductance by uncoupling protein 1 in yeast mitochondria.
abstract: Q (coenzyme Q or ubiquinone) is reported to be a cofactor obligatory for proton transport by UCPs (uncoupling proteins) in liposomes [Echtay, Winkler and Klingenberg (2000) Nature (London) 408, 609-613] and for increasing the binding of the activator retinoic acid to UCP1 [Tomás, Ledesma and Rial (2002) FEBS Lett. 526, 63-65]. In the present study, yeast ( Saccharomyces cerevisiae ) mutant strains lacking Q and expressing UCP1 were used to determine whether Q was required for UCP function in mitochondria. Wild-type yeast strain and two mutant strains (CENDeltaCOQ3 and CENDeltaCOQ2), both not capable of synthesizing Q, were transformed with the mouse UCP1 gene. UCP1 activity was measured as fatty acid-dependent, GDP-sensitive proton conductance in mitochondria isolated from the cells. The activity of UCP1 was similar in both Q-containing and -deficient yeast mitochondria. We conclude that Q is neither an obligatory cofactor nor an activator of proton transport by UCP1 when it is expressed in yeast mitochondria.
authors.affiliation: MRC Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, UK. telma.esteves@mrc-dunn.cam.ac.uk
authors.forename: Telma C
authors.initials: TC
authors.lastname: Esteves
authors.forename: Karim S
authors.initials: KS
authors.lastname: Echtay
authors.forename: Tanya
authors.initials: T
authors.lastname: Jonassen
authors.forename: Catherine F
authors.initials: CF
authors.lastname: Clarke
authors.forename: Martin D
authors.initials: MD
authors.lastname: Brand
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D007473:Ion Channels; D017136:Ion Transport; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D009154:Mutation; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D014170:Transformation, Genetic; D014451:Ubiquinone / Q000502:physiology*; D000071256:Uncoupling Protein 1
chemical_list: D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011522:Protons; C000604371:UCP1 protein, human; C000604372:Ucp1 protein, mouse; D000071256:Uncoupling Protein 1; D014451:Ubiquinone