Ubiquinone reduction in the photosynthetic reaction centre of <i>Rhodobacter sphaeroides</i>: interplay between electron transfer, proton binding and flips of the quinone ring

Mulkidjanian, Armen Y.; Kozlova, Maria; Cherepanov, Dmitry A.

doi:10.1042/bst0330845

Cited by 21 publications

(16 citation statements)

References 53 publications

(99 reference statements)

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“…the reorientation of the Ser223 residue in the vicinity of the Q B binding site [26,27]. The latter conformational changes may likely be possible only upon activation of molecular dynamics as a "lubricant" [10,13].…”

Section: Dynamics-function Correlationmentioning

confidence: 99%

The functional role of protein dynamics in photosynthetic reaction centers investigated by elastic and quasielastic neutron scattering

Pieper

2015

EPJ Web of Conferences

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Abstract. This short review summarizes our current knowledge about the functional relevance of protein dynamics in photosynthetic reaction centers. In the case of Photosystem II membrane fragments, elastic and quasielastic neutron scattering experiments reveal a dynamical transition at about 240 K corresponding to the activation of picosecond molecular motions. Likewise, a "freezing" of molecular dynamics is observed upon dehydration. Intriguingly, these effects correlate with the pronounced temperature-and hydration-dependence of specific electron transfer steps in Photosystem II indicating that molecular dynamics is an indispensable prerequisite for its function. Thus, electron transfer in Photosystem II appears to be a prototypical example for a dynamics-function correlation. Finally, the laser-neutron pump-probe technique is shown to permit in-situ monitoring of molecular dynamics in specific functional states of a protein in real time.

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Section: Dynamics-function Correlationmentioning

confidence: 99%

The functional role of protein dynamics in photosynthetic reaction centers investigated by elastic and quasielastic neutron scattering

Pieper

2015

EPJ Web of Conferences

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“…The independence of the transfer rate on the driving force for electron transfer (9) has led to the proposal that the reaction is conformationally gated (for review see ref. 24). …”

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confidence: 99%

Trapped Conformational States of Semiquinone (D⁺^•Q_B^-^•) Formed by B-Branch Electron Transfer at Low Temperature in Rhodobacter sphaeroides Reaction Centers

et al. 2006

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The reaction center (RC) from Rhodobacter sphaeroides captures light energy by electron transfer between quinones Q A and Q B , involving a conformational gating step. In this work, conformational states of D +• Q B −• were trapped (80K) and studied using EPR spectroscopy in mutant RCs that lack Q A in which Q B was reduced by the bacteriopheophytin along the B-branch. In mutant RCs frozen in the dark, a light induced EPR signal due to D +• Q B −• formed in 30% of the sample with low quantum yield (0.2%-20%) and decayed in 6 s. A small signal with similar characteristics was also observed in native RCs. In contrast, the EPR signal due to D + Q B − in mutant RCs illuminated while freezing formed in ~ 95% of the sample that did not decay (τ >10 7 s) at 80K. In all samples, the observed gvalues were the same (g=2.0026) indicating that all active Q B −• was located in a proximal conformation coupled with the non-heme Fe 2+ . We propose that before electron transfer at 80K, the majority (~70%) of Q B , structurally located in the distal site, cannot be stably reduced, while the minor ( can be considered to be the initial and final states along the reaction coordinate for conformationallygated electron transfer.

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“…The reduction of QA occurs rapidly (r-0.2 ns) with a quantum yield of 98% [19], has a rate of formation that is almost temperature independent and proceeds even at cryogenic temperatures. Subsequent electron transfer from QA" to a secondary quinone QB is more complex [20,21]. Ir occurs on a slower time scale (r-100 ~ts) [22], is temperature dependent and does not proceed at cryogenic temperature if the RCs are frozen in the dark [23,24].…”

Section: Introductionmentioning

confidence: 99%

Light-induced EPR spectra of reaction centers fromRhodobacter sphaeroides at 80 K: Evidence for reduction of QB by B branch electron transfer in native reaction centers

et al. 2007

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Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides capture solar energy by electron transfer from primary donor, D, to quinone acceptor, Q(B,) through the active A-branch of electron acceptors, but not the inactive B-branch. The light induced EPR spectrum from native RCs that had Fe(2+) replaced by Zn(2+) was investigated at cryogenic temperature (80K, 35 GHz). In addition to the light induced signal due to formation of D(+•)Q(A) (-•) observed previously, a small fraction (~5%) of the signal displayed very different characteristics: (1) The signal was absent in RCs in which the Q(B) was displaced by the inhibitor stigmatellin. (2) Its decay time (τ=6 s) was the same as observed for D(+•)Q(B) (-•) in mutant RCs lacking Q(A,) which is significantly slower than for D(+•)Q(A) (-•) (τ=30 ms). (3) Its EPR spectrum was identical to that of D(+•)Q(B) (-•). (4) The quantum efficiency for forming the major component of the signal was the same as that found for mutant RCs lacking Q(A) (Φ =0.2%) and was temperature independent. These results are explained by direct photochemical reduction of Q(B)via B-branch electron transfer in a small fraction of native RCs.

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Ubiquinone reduction in the photosynthetic reaction centre of Rhodobacter sphaeroides: interplay between electron transfer, proton binding and flips of the quinone ring

Cited by 21 publications

References 53 publications

The functional role of protein dynamics in photosynthetic reaction centers investigated by elastic and quasielastic neutron scattering

The functional role of protein dynamics in photosynthetic reaction centers investigated by elastic and quasielastic neutron scattering

Trapped Conformational States of Semiquinone (D⁺^•Q_B^-^•) Formed by B-Branch Electron Transfer at Low Temperature in Rhodobacter sphaeroides Reaction Centers

Light-induced EPR spectra of reaction centers fromRhodobacter sphaeroides at 80 K: Evidence for reduction of QB by B branch electron transfer in native reaction centers

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Ubiquinone reduction in the photosynthetic reaction centre of Rhodobacter sphaeroides: interplay between electron transfer, proton binding and flips of the quinone ring

Cited by 21 publications

References 53 publications

The functional role of protein dynamics in photosynthetic reaction centers investigated by elastic and quasielastic neutron scattering

The functional role of protein dynamics in photosynthetic reaction centers investigated by elastic and quasielastic neutron scattering

Trapped Conformational States of Semiquinone (D+•QB-•) Formed by B-Branch Electron Transfer at Low Temperature in Rhodobacter sphaeroides Reaction Centers

Light-induced EPR spectra of reaction centers fromRhodobacter sphaeroides at 80 K: Evidence for reduction of QB by B branch electron transfer in native reaction centers

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Trapped Conformational States of Semiquinone (D⁺^•Q_B^-^•) Formed by B-Branch Electron Transfer at Low Temperature in Rhodobacter sphaeroides Reaction Centers