Functioning of quinone acceptors in the reaction center of the green photosynthetic bacterium <i>Chloroflexus aurantiacus</i>

Kutuzov, Mikhail A.; Mamedov, Mahir D.; Semenov, Alexey Yu.; Shinkarev, Vladimir P.; Verkhovsky, Michael I.; Abdulaev, N.G.; Drachev, Lel A.

doi:10.1016/0014-5793(91)81064-f

Cited by 6 publications

(2 citation statements)

References 10 publications

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“…Proteoliposomes were prepared according to Ref. [13]. The flash‐induced voltage generation was traced by capacitive potentiometry, as described in detail elsewhere [10,14].…”

Section: Methodsmentioning

confidence: 99%

Proton transfer in the photosynthetic reaction center of Blastochloris viridis

et al. 2007

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Photosynthetic reaction centers of Blastochloris viridis require two quanta of light to catalyse a two-step reduction of their secondary ubiquinone Q B to ubiquinol. We employed capacitive potentiometry to follow the voltage changes that were caused by the accompanying transmembrane proton displacements. At pH 7.5 and 20°C, the Q B -related voltage generation after the first flash was contributed by a fast, temperature-independent component with a time constant of $30 ls and a slower component of $200 ls with activation energy (E a ) of 50 kJ/mol. The kinetics after the second flash featured temperature-independent components of 5 ls and 200 ls followed by a component of 600 ls with E a $ 60 kJ/mol.

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“…Proteoliposomes were prepared according to Ref. [13]. The flash‐induced voltage generation was traced by capacitive potentiometry, as described in detail elsewhere [10,14].…”

Section: Methodsmentioning

confidence: 99%

Proton transfer in the photosynthetic reaction center of Blastochloris viridis

et al. 2007

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“…Reaction center reconstitution in proteoliposomes RC reconstitution in liposomes was accomplished following the procedure outlined in [19][20][21]. One to eight milligrams of 1,2-diacyl-sn-glycero-3-phosphocholine (used at 48% purity, Sigma) were dissolved in 500 lL of chloroform to which, when needed, aliquots of a 1 mM ubiquinone-10 (Sigma) solution were added.…”

Section: Isolation Of Reaction Centers and Q B Site Depletionmentioning

confidence: 99%

Kinetics of the quinone binding reaction at the Q_B site of reaction centers from the purple bacteria Rhodobacter sphaeroides reconstituted in liposomes

Milano

Agostiano

Mavelli

et al. 2003

European Journal of Biochemistry

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Transmembrane proton translocation in the photosynthetic membranes of the purple bacterium Rhodobacter sphaeroides is driven by light and performed by two transmembrane complexes; the photosynthetic reaction center and the ubiquinol–cytochrome c oxidoreductase complex, coupled by two mobile electron carriers; the cytochrome and the quinone. This paper focuses on the kinetics and thermodynamics of the interaction between the lipophylic electron carrier ubiquinone‐10 and the photosynthetic enzyme reconstituted in liposomes. The collected data were simulated with an existing recognized kinetic scheme [Shinkarev, V.P. & Wraight, C.A. (1993) In The Photosynthetic Reaction Center (Deisenhofer, J. & Norris, J.R., eds.), pp. 193–255. Academic Press, San Diego, CA, USA] and the kinetic constants of the uptake (7.2 × 107 m−1·s−1) and release (40 s−1) processes of the ligand were inferred. The results obtained for the quinone release kinetic constant are comparable to the rate of the charge recombination reaction from the state D+QA–. Values for the kinetic constants are discussed as part of the overall photocycle, suggesting that its bottleneck may not be the quinone uptake reaction in agreement with a previous report (Gerencser, L., Laczko, G. & Maróti, P. (1999) Biochemistry38, 16866–16875).

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Photosynthetic electrogenic events in native membranes ofChloroflexus aurantiacus. Flash-induced charge displacements within the reaction center-cytochromec 554 complex

Venturoli¹,

Hochkoeppler²,

Zannoni³

et al. 1994

Photosynth Res

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The thermophilic phototrophChloroflexus aurantiacus possesses a photosynthetic reaction center (RC) containing a pair of menaquinones as primary (QA) and secondary (QB) electron acceptors and a bacteriochlorophyll dimer (P) as a primary donor. A tetraheme cytochromec 554 with two high(H)- and two low(L)-potential hemes operates as an immediate electron donor for P. The following equilibrium Em,7 values were determined by ESR for the hemes in whole membrane preparations: 280 mV (H1), 150 mV (H2), 95 mV (L1) and 0 mV (L2) (Van Vliet et al. (1991) Eur. J. Biochem. 199: 317-323). Partial electrogenic reactions induced by a laser flash inChl. aurantiacus chromatophores adsorbed to a phospholipid-impregnated collodion film were studied electrometrically at pH 8.3. The photoelectric response included a fast phase of ΔΨ generation (τ < 10 ns, phase A). It was ascribed to the charge separation between P(+) and QA (-) as its amplitude decreased both at high and low Eh values (Em,high=360±10 mV, estimated Em,low∼\s-160 mV) in good agreement with Em values for P/P(+) and QA/QA (-) redox couples. A slower kinetic component appeared upon reduction of the cytochromec 554 hemes (phase C). With H1 reduced before the flash the amplitude of phase C was equal to 15-20% of that of phase A and its rise time was 1.2-1.3 μs: we attribute this phase to the electrogenic electron transfer from H1 to P(+). Pre-reduction of H2 decreased the τ value to about 700-800 ns and increased the amplitude of phase C to 30-35% of that of phase A. Pre-reduction of L1 further accelerated phase C (up to τ of 500 ns) and induced a reverse electrogenic phase with τ of 12 μs and amplitude equal to 10% of phase A. Upon pre-reduction of L2 the rise time of phase C was decreased to about 300 ns and its amplitude decreased by 30%. The acceleration in the onset of phase C is explained by the acceleration of the rate-limiting H1 ⇒ P electrogenic reaction after reduction of the other hemes due to their electrostatic influence; a P-H1-(L1-L2)-H2 alignment of redox centers with an approximately rhombic arrangement of the cytochromec 554 hemes is proposed. The observed reverse phase is ascribed to the post-flash charge redistribution between the hemes. Redox titration of the amplitude of phase C yielded the Em,8.3 values of H1, H2 and L2 hemes: 340±10 mV for H1, 160±20 mV for H2 and -40±40 mV for L2.

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Functioning of quinone acceptors in the reaction center of the green photosynthetic bacterium Chloroflexus aurantiacus

Cited by 6 publications

References 10 publications

Proton transfer in the photosynthetic reaction center of Blastochloris viridis

Proton transfer in the photosynthetic reaction center of Blastochloris viridis

Kinetics of the quinone binding reaction at the Q_B site of reaction centers from the purple bacteria Rhodobacter sphaeroides reconstituted in liposomes

Photosynthetic electrogenic events in native membranes ofChloroflexus aurantiacus. Flash-induced charge displacements within the reaction center-cytochromec 554 complex

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Functioning of quinone acceptors in the reaction center of the green photosynthetic bacterium Chloroflexus aurantiacus

Cited by 6 publications

References 10 publications

Proton transfer in the photosynthetic reaction center of Blastochloris viridis

Proton transfer in the photosynthetic reaction center of Blastochloris viridis

Kinetics of the quinone binding reaction at the QB site of reaction centers from the purple bacteria Rhodobacter sphaeroides reconstituted in liposomes

Photosynthetic electrogenic events in native membranes ofChloroflexus aurantiacus. Flash-induced charge displacements within the reaction center-cytochromec 554 complex

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Kinetics of the quinone binding reaction at the Q_B site of reaction centers from the purple bacteria Rhodobacter sphaeroides reconstituted in liposomes