S66 ABSTRACTS / Biochimica et Biophysica Acta 1777 (2008) S2–S111
S11/3 Carboxyl group functions in the heme-copper oxidases:Information from mid-ir vibrational spectroscopyPeter R. Rich, Amandine MaréchalGlynn Laboratory of Bioenergetics, Department of Biology, UniversityCollege London, Gower Street, London WC1E 6BT, UK
E-mail: [email protected]
Carboxyl groups of possible functional importance in bovine andbacterial cytochrome c oxidases (CcO) are reviewed and assessed. A criticalanalysis is presented of availablemid-infrared vibrational data that pertainto these functional carboxyl groups. These data and their interpretationsare discussed in relation to current models of the mechanism of protonand electron coupling in the protonmotive CcO superfamily.
doi:10.1016/j.bbabio.2008.05.258
S11/4 Fast ligand and electron transfer dynamics in oxidases andcytochrome cMarten H. VosLaboratoire d'Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128Palaiseau, FranceINSERM U696, F-91128 Palaiseau, France
E-mail: [email protected]
The active site of heme-copper oxidases contains two cofactors,heme a3 and CuB, which can both bind external ligands as the substrateO2 and signallingmoleculesNO and CO, andwhich are both involved inelectron transfer processes. Over the last few years we have exploitedthe fact that the heme-ligand bond can be dissociated by a short lightpulse to explore the dynamics of CO and NO in the active site and theinteraction between the two cofactors using ultrafast spectroscopictechniques. For example, we have time-resolved the CO transfer fromheme a3 to CuB and shown that it occurs in a ballistic way in ∼500 fs,which presumably reflects rigidity of the active site. Heme a is locatedclose to heme a3 (∼7Å edge-to-edge) and acts as electron donor for theactive site. Using mixed valence oxidases we have extended the‘reverse electron flow’ technique to the ultrafast regime and demon-strated that this electron transfer process occurs in only 1.2 ns. Theprocess is activationless and associated with a very low reorganizationenergy (b200meV), in contrast to common assumptions but in generalagreementwith the hydrophobic environment of the reactants. Finally,ligand dynamics in native and modified cytochrome c reflects therigidity required for optimal electron transfer properties.
doi:10.1016/j.bbabio.2008.05.259
S11/5 The role of the conserved tryptophan272 of the Paracoccusdenitrificans cytochrome c oxidase in proton pumpingSimon de VriesDepartment of Biotechnology, Delft University of Technology, Julianalaan67, 2628 BC, Delft, The Netherlands
E-mail: [email protected]
The superfamily of heme-copper oxidases comprises the cyto-chrome oxidases and the NO reductases, the former catalyzing thereduction of molecular oxygen to water, the latter the reduction of NOto N2O. Cytochrome oxidases are the final electron acceptors in therespiratory chains of bacteria, archaea andmitochondria. Based on thestructure of its D- and K-proton pathways cytochrome aa3 from Par-acoccus denitrificans, has been classified as a Type A oxidase. Thereduction of oxygen generates a proton electrochemical gradientacross the cytoplasmic membrane. Four protons are used for the
formation of water (chemical protons) and four are pumped across themembrane. The chemical protons join with electrons and O2 at theheme a3-CuB binuclear center yielding water. The thermodynamics ofthe chemical protons can be understood on basis of the chemical,redox and acid-base properties of the metallo-binuclear center.However, what constitutes the driving force for the pumped protons?Our recentmicrosecond freeze-hyperquenching experiments revealedthe formation of a transient tryptophan radical derived from thestrictly conserved W272 in the transition F → FW⁎ → OH. We proposethat the redoxchemistry and acid/base properties ofW272 provide thethermodynamic and directional force for proton pumping by thecytochrome oxidases.
doi:10.1016/j.bbabio.2008.05.260
S11/6 Looking for the minimum common denominator inhaem-copper oxygen reductases: Towards a unified catalyticmechanismManuelaM. Pereira, Filipa L. Sousa, Andreia F. Veríssimo,Miguel TeixeiraInstituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa,Av. da República – EAN, 2780-157 Oeiras, Portugal
E-mail: m perei ra @i tq b .un l.pt
Haem-copper oxygen reductases are transmembrane proteincomplexes that reduce oxygen to water and pump protons acrossthe mitochondrial or periplasmatic membrane, contributing to thetransmembrane electrochemical potential. Seven years ago weproposed a classification of these enzymes into three different families(A, B and C), based on the constituents of their proton channels, latersupported by the so far identified characteristics of the catalytic centreof each family members. The members of the three families have incommon the same general structural fold, the same or analogousprosthetic groups and the existence of proton channels, in thecatalytic subunit. These observations raise the hypothesis that themechanisms for oxygen reduction, proton pumping and coupling maybe the same for all haem-copper oxygen reductases. Under thishypothesis they should be performed and controlled by the same orequivalent elements/events. The identification of retained elements inall families will reveal their importance and may prompt thedefinition of the enzyme operating mode. Thus the search for aminimum common denominator may have a crucial importance. Inthis article we highlight what is already established for the haem-copper oxygen reductases and emphasize the main questions stillunanswered in a comprehensive basis.
doi:10.1016/j.bbabio.2008.05.261
S11/7 The mechanism of haem copper oxidases studied by EPRspectroscopyFraser MacMillana, Heike Angererb, Martin Kauppc, Christian Teutloffa,Hartmut MichelbaHenry Wellcome Unit of Biological EPR, School of Chemical Sciences,University of East Anglia, Norwich, UKbMax Planck Institute of Biophysics, Frankfurt, Universität Würzburg,Würzburg, GermanycInstitut für Anorganische Chemie, Universität Würzburg,Würzburg, Germany
E-mail: [email protected]
Haem copper oxidases constitute the terminal complex of therespiratory chain and catalyses the four electron reduction of dioxygento water. This is an extremely exergonic redox reaction which iscoupled to protonpumping across the innermitochondrial or bacterial
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