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How rapid are the internal reactions of the ubiquinol:cytochrome c 2 oxidoreductase?

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Abstract

The temperature dependence of the partial reactions leading to turn-over of the UQH2:cyt c 2 oxidoreductase of Rhodobacter sphaeroides have been studied. The redox properties of the cytochrome components show a weak temperature dependence over the range 280–330 K, with coefficients of about 1 m V per degree; our results suggest that the other components show similar dependencies, so that no significant change in the gradient of standard free-energy between components occurs over this temperature range. The rates of the reactions of the high potential chain (the Rieske iron sulfur center, cytochromes c 1 and c 2, reaction center primary donor) show a weak temperature dependence, indicating an activation energy < 8 kJ per mole for electron transfer in this chain. The oxidation of ubiquinol at the Qz-site of the complex showed a strong temperature dependence, with an activation energy of about 32 kJ mole−1. The electron transfer from cytochrome b-566 to cytochrome b-561 was not rate determining at any temperature, and did not contribute to the energy barrier. The activation energy of 32 kJ mole−1 for quinol oxidation was the same for all states of the quinone pool (fully oxidized, partially reduced, or fully reduced before the flash). We suggest that the activation barrier is in the reaction by which ubiquinol at the catalytic site is oxidized to semiquinone. The most economical scheme for this reaction would have the semiquinone intermediate at the energy level indicated by the activation barrier. We discuss the plausibility of this simple model, and the values for rate constants, stability constant, the redox potentials of the intermediate couples, and the binding constant for the semiquinone, which are pertinent to the mechanism of the ubiquinol oxidizing site.

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Abbreviations

(BChl)2 :

P870, primary donor of the photochemical reaction center

b/c 1 complex:

ubiquinol: cytochrome c 2 oxidoreductase

cyt b H :

cytochrome b-561 or higher potential cytochrome b

cyt b L :

cytochrome b-566, or low potential cytochrome b

cyt c 1, cyt c 2, cyt c t :

cytochromes c 1 and c 2, and total cytochrome c (cyt c 1 and cyt c 2)

Fe.S:

Rieske-type iron sulfur center, Q

QH2 :

ubiquinone, ubiquinol

Qz, QzH2, Qz − :

ubiquinone, ubiquinol, and semiquinone anion of ubiquinone, bound at quinol oxidizing site

Qz-site:

ubiquinol oxidizing site (also called Qo-(outside)

Qo :

(Oxidizing)

QP :

(Positive proton potential) site)

Qc-site:

uubiquinone reductase site (also called the Qi-(inside)

QR :

(Reducing), or

QN :

(Negative proton potential) site)

UHDBT:

5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazol

References

  • Andrews KM (1988) Purification and characterization of the cytochrome bc 1 complex from Rhodobactor sphaeroides. Ph.D Thesis, University of Illinois, Urbana

    Google Scholar 

  • Bowyer JR, Tierney GV and Crofts AR (1979a) Secondary electron transfer in chromatophores of Rhodopseudomonas capsulata ala pho+. FEBS Lett 101: 201–206

    Google Scholar 

  • Bowyer JR, Tierney GV and Crofts AR (1979b) Cytochrome c 2-reaction centre coupling in chromatophores of Rhodopseudomonas sphaeroides and Rhodopseudomonas capsulata. FEBS Lett 101: 207–212

    Google Scholar 

  • Clark WM (1972) Oxidation-reduction Potentials of Organic Systems. Huntington: Robert E. Krieger Publishing

    Google Scholar 

  • Crofts AR, Crowther D and Tierney GV (1975) Electrogenic electron transport in photosynthetic bacteria. In: Quagliariello E, Papa S, Palmieri F, Slater EC and Siliprandi N (eds) Electron Transfer Chains and Oxidative Phosphorylation, pp 233–241. Amsterdam: North-Holland Publ. Co./Elsevier

    Google Scholar 

  • Crofts AR, Meinhardt SW, Jones KR and Snozzi M (1983) The role of the quinone pool in the cyclic electron-transfer chain of Rhodobactor sphaeroides. Biochim Biophys Acta 723: 202–218

    Google Scholar 

  • Crofts AR and Wraight CA (1983) The electrochemical domain of photosynthesis. Biochim Biophys Acta 726: 149–185

    Google Scholar 

  • Crofts AR, Robinson HH and Snozzi M (1984) Reaction of quinones at catalytic sites; a diffusional role in H-transfer. In: Sybesma C (ed.) Advances in Photosynthesis Research, pp I: 461–468. The Hague: Martinus Nijhoff/Dr W Junk Publishers

    Google Scholar 

  • Crofts AR (1985) The mechanism of the ubiquinol:cytochrome c oxidoreductases of mitochondria and of Rhodopseudomonas sphaeroides. In: Martonosi A (ed.) The Enzymes of Biological Membranes, 2nd edn, pp 347–382. New York: Plenum Press

    Google Scholar 

  • Crofts AR (1986) Reaction center and UQH2:cyt c 2 oxidoreductase act as independent enzymes in Rps. sphaeroides. J Bioenerg Biomemb 18: 437–445

    Google Scholar 

  • De Vries S, Albracht SPJ, Berden JA and Slater EC (1981) A new species of bound ubisemiquinone anion in QH2:cytochrome c oxidoreductase. J Biol Chem 256: 11996–11998

    Google Scholar 

  • De Vries S, Albracht SPJ, Berden JA and Slater EC (1982) The pathway of electrons through QH2:cytochrome c oxidoreductase studied by pre-steady state kinetics, Biochim Biophys Acta 681: 41–53

    Google Scholar 

  • De Vries S (1983) The pathway of electrons in QH2:cytochrome c Oxidoreductase. Ph.D. thesis, University of Amsterdam, Amsterdam

    Google Scholar 

  • De Vries S and Dutton PL (1985) Electron flow in QH2: c oxidoreductase as studied in a hybrid system. In: Quagliariello E, Slater EC, Saccone C and Kroon AM (eds.) Achievements and Perspectives of Mitochondrial Research, pp 103–110 Amsterdam: Elsevier

    Google Scholar 

  • Dutton PL (1978) Redox potentionmentric determination of midpoint potentials of oxidation-reduction components of biological electron transfer systems. Meths Enzymol 54 411–435

    Google Scholar 

  • Dutton PL (1986) Energy Transduction in anoxygenic photosynthesis. In: Staehelin A and Arntzen CJ (eds) Encyclopedia of Plant Biology, Vol. 19, pp 197–237. Berlin: Springer-Verlag

    Google Scholar 

  • Glaser EG and Crofts AR (1984) A new electrogenic step in the ubiquinol:cytochrome c 2 oxidoreductase complex of Rhodobacter sphaeroides. Biochim Biophys Acta 766: 322–333

    Google Scholar 

  • Glaser EG and Crofts AR (1987) Studies of the electrogenicity of the reduction of cytochrome b561 through the antimycinsensitive site of the ubiquinol-cytochrome c 2 oxidoreductase complex of Rhodobacter sphaeroides. In: Papa P, Chance B, and Ernster L (eds) Cytochrome Systems: Molecular Biology and Bioenergetics, pp 625–631. New York: Plenum Press

    Google Scholar 

  • Jones RW and Whitmarsh J (1985) Origin of the electrogenic reaction in the chloroplast cytochrome b-f complex. Photobiochem Photobiophys 9: 119–128

    Google Scholar 

  • Kohn A (1988) Hidden Figures. The Scientist, Nov 14th, p. 11

  • Meinhardt SW and Crofts AR (1983) The role of the cytochrome b-566 in the cyclic electron-transfer chain of Rhodobactor sphaeroides. Biochim Biophys Acta 723: 219–230

    Google Scholar 

  • Meinhardt SW and Crofts AR (1982a) The site and mechanism of action of myxothiazol as an inhibitor of electron transfer in Rhodopseudomonas sphaeroides. FEBS Lett 149: 217–222

    Google Scholar 

  • Meinhardt SW and Crofts AR (1982b) Kinetic and thermodynamic resolution of cytochrome c 1 and cytochrome c 2 from Rhodopseudomonas sphaeroides. FEBS Lett 149: 223–227.

    Google Scholar 

  • Mitchell PM (1976) Possible molecular mechanism of the protonmotive function of cytochrome systems. J Theoret Biol 62: 327–367

    Google Scholar 

  • Prince RC and Dutton PL (1977) Single and multiple turnover reactions in the ubiquinone cytochrome b-c 2 oxidoreductase of Rhodopseudomonas sphaeroides. The physical chemistry of the major electron donor to cytochrome c 2 and its coupled reactions. Biochim Biophys Acta 462: 731–747

    Google Scholar 

  • Prince RC, Bashford CL, Takamiya K-I, van den Berg WH and Dutton PL (1978) Second-order kinetics of the reduction of cytochrome c 2 by the ubiquinone cytochrome b-c 2 oxidoreductase of Rhodopseudomonas sphaeroides. J Biol Chem 253: 4137–4142

    Google Scholar 

  • Robertson DE and Dutton PL (1988) The nature and magnitude of the charge-separation reactions of ubiquinol cytochrome c 2 oxidoreductase. Biochim Biophys Acta 935: 273–291

    Google Scholar 

  • Selak MA and Whitmarsh J (1982) Kinetics of the electrogenic step and cytochrome b 6 and f redox changes in chloroplasts. FEBS Lett 150: 286–292

    Google Scholar 

  • Selak MA and Whitmarsh J (1984) Charge transfer from photosystem I to the cytochrome b/f complex: diffusion and membrane lateral heterogeneity. Photochem Photobiol 39: 485–489

    Google Scholar 

  • Snozzi M and Crofts AR (1985) Kinetics of the c-cytochromes in chromatophores from Rhodopseudomonas sphaeroides as a function of the concentration of cytochrome c 2. Influence of this concentration on the oscillation of the secondary acceptor of the reaction center QB. Biochim Biophys Acta 809: 260–270

    Google Scholar 

  • T'sai A-L, Olson JS and Palmer G (1983) The oxidation of yeast complex III. Evidence for a very rapid electron equilibration between cytochrome c 1 and the iron-sulfur center. J Biol Chem 258: 2122–2125

    Google Scholar 

  • Venturoli G, Fernandez-Velasco JG, Crofts AR and Melandri BA (1986) Demonstration of a collisional interaction of ubiquinol with the ubiquinol-cytochrome c 2 oxidoreductase complex in chromatophores from Rhodobacter sphaeroides. Biochim Biophys Acta 851: 340–352

    Google Scholar 

  • Venturoli G, Fernandez-Velasco JG, Crofts AR and Melandri BA (1988) The effect of the size of the quinone pool on the electrogenic reactions in the ubiquinol-cytochrome c 2 oxidoreductase of Rhodobacter capsulatus. Pool behaviour at the quinone reductase site. Biochim Biophys Acta 935: 258–272

    Google Scholar 

  • Wang Z, Berry EA and Crofts AR (1987) Electron transfer from quinol to cytochrome b-561 is not diffusion limited in the ubiquinol-cytochrome c 2 oxidoreductase complex of Rps. sphaeroides. In: Biggins J (ed) Progress in Photosynthesis Research, pp 2: 493–496. Dordrecht: Martinus Nijhoff Publishers

    Google Scholar 

  • Wraight CA (1981) Oxidation-reduction physical chemistry of the acceptor quinone complex in bacterial photosynthetic reaction center: Evidence for a new model of herbicide activity, Israel J Chem 21: 348–354

    Google Scholar 

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Authors and Affiliations

  1. Department of Physiology and Biophysics, University of Illinois at Urbana-Champaign, 524 Burrill Hall, 407 S. Goodwin Street, 61801, Urbana, Il, U.S.A.

    Antony R. Crofts & Zhenggan Wang

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  1. Antony R. Crofts
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  2. Zhenggan Wang
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Crofts, A.R., Wang, Z. How rapid are the internal reactions of the ubiquinol:cytochrome c 2 oxidoreductase?. Photosynth Res 22, 69–87 (1989). https://doi.org/10.1007/BF00114768

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  • DOI: https://doi.org/10.1007/BF00114768

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