title: Structural Changes and Proton Transfer in Cytochrome c Oxidase.
abstract: In cytochrome c oxidase electron transfer from cytochrome c to O2 is linked to transmembrane proton pumping, which contributes to maintaining a proton electrochemical gradient across the membrane. The mechanism by which cytochrome c oxidase couples the exergonic electron transfer to the endergonic proton translocation is not known, but it presumably involves local structural changes that control the alternating proton access to the two sides of the membrane. Such redox-induced structural changes have been observed in X-ray crystallographic studies at residues 423-425 (in the R. sphaeroides oxidase), located near heme a. The aim of the present study is to investigate the functional effects of these structural changes on reaction steps associated with proton pumping. Residue Ser425 was modified using site-directed mutagenesis and time-resolved spectroscopy was used to investigate coupled electron-proton transfer upon reaction of the oxidase with O2. The data indicate that the structural change at position 425 propagates to the D proton pathway, which suggests a link between redox changes at heme a and modulation of intramolecular proton-transfer rates.
authors: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
authors: Jóhanna
authors: J
authors: Vilhjálmsdóttir
authors: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
authors: Ann-Louise
authors: AL
authors: Johansson
authors: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
authors: Peter
authors: P
authors: Brzezinski
mesh_terms: D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D010637:Phenolsulfonphthalein / Q000378:metabolism; D017494:Proton Pumps / Q000378:metabolism; D011522:Protons; D012242:Rhodobacter sphaeroides / Q000201:enzymology*
chemical_list: D017494:Proton Pumps; D011522:Protons; D003576:Electron Transport Complex IV; D010637:Phenolsulfonphthalein; D010100:Oxygen