title: Reaction of S. cerevisiae mitochondria with ligands: Kinetics of CO and O2binding to flavohemoglobin and cytochrome c oxidase.
abstract: Kinetic methods used to investigate electron and proton transfer within cytochrome c oxidase (CytcO) are often based on the use of light to dissociate small ligands, such as CO, thereby initiating the reaction. Studies of intact mitochondria using these methods require identification of proteins that may bind CO and determination of the ligand-binding kinetics. In the present study we have investigated the kinetics of CO-ligand binding to S. cerevisiae mitochondria and cellular extracts. The data indicate that CO binds to two proteins, CytcO and a (yeast) flavohemoglobin (yHb). The latter has been shown previously to reside in both the cell cytosol and the mitochondrial matrix. Here, we found that yHb resides also in the intermembrane space and binds CO in its reduced state. As observed previously, we found that the yHb population in the mitochondrial matrix binds CO, but only after removal of the inner membrane. The mitochondrial yHb (in both the intermembrane space and the matrix) recombines with CO with τ≅270ms, which is significantly slower than observed with the cytosolic yHb (main component τ≅1.3ms). The data indicate that the yHb populations in the different cell compartments differ in structure.
authors.affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Markus L
authors.initials: ML
authors.lastname: Björck
authors.affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Shu
authors.initials: S
authors.lastname: Zhou
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 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. Electronic address: peterb@dbb.su.se.
authors.forename: Peter
authors.initials: P
authors.lastname: Brzezinski
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D049308:Dioxygenases / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006420:Hemeproteins / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D006420:Hemeproteins; D008024:Ligands; D011522:Protons; D029701:Saccharomyces cerevisiae Proteins; D002248:Carbon Monoxide; D049308:Dioxygenases; C101796:YHB1 protein, S cerevisiae; D003576:Electron Transport Complex IV; D010100:Oxygen
keywords: Cytochrome aa(3); Electron transfer; Kinetics; Ligand; Mechanism; Membrane protein; Yeast