Light-Induced Charge Separation in Photosynthetic Bacterial Reaction Centers Monitored by FTIR Difference Spectroscopy: the QA Vibrations

Breton, Jacques; Burie, Jean-René; Berthomieu, Catherine; Thibodeau, D. L.; Andrianambinintsoa, S.; Dejonghe, D.; Berger, G.; Nabedryk, E.

doi:10.1007/978-1-4615-3050-3_19

Cited by 14 publications

(11 citation statements)

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“…viridis appear at 1,653 and 1,637 cm Ϫ1 due to different interactions of the carbonyls with the protein. One of these modes had been previously proposed at 1,636 cm Ϫ1 (31 (Fig. 3) or with ubiquinone-6 (Fig.…”

Section: Discussionmentioning

confidence: 72%

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Efficient exchange of the primary quinone acceptor Q _A in isolated reaction centers of Rhodopseudomonas viridis

Breton

1997

Proc. Natl. Acad. Sci. U.S.A.

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USA 88, 3491-3495], who were able to extract with detergents the firmly bound ubiquinone Q A from the RC of Rhodobacter sphaeroides and reconstitute the site with extraneous quinones. Up to now a comparable protocol was lacking for the RC of Rhodopseudomonas viridis despite the fact that its Q A site, which contains 2-methyl-3-nonaprenyl-1,4-naphthoquinone (menaquinone-9), has provided the best x-ray structure available. Fourier transform infrared difference spectroscopy, together with the use of isotopically labeled quinones, can probe the interaction of Q A with the RC protein. We establish that a simple incubation procedure of isolated RCs of Rp. viridis with an excess of extraneous quinone allows the menaquinone-9 in the Q A site to be almost quantitatively replaced either by vitamin K 1 , a close analogue of menaquinone-9, or by ubiquinone. To our knowledge, this is the first report of quinone exchange in bacterial photosynthesis. The Fourier transform infrared data on the quinone and semiquinone vibrations show a close similarity in the bonding interactions of vitamin K 1 with the protein at the Q A site of Rp. viridis and Rb. sphaeroides, whereas for ubiquinone these interactions are significantly different. The results are interpreted in terms of slightly inequivalent quinone-protein interactions by comparison with the crystallographic data available for the Q A site of the two RCs.In the reaction center (RC) of photosynthetic purple bacteria, two quinone molecules (Q A and Q B ) play an essential role in coupling the electron-and proton-transfer reactions leading to the conversion of light energy into chemical energy (for a review, see ref. 1). Following absorption of a photon, transmembrane electron transfer occurs between a dimer of bacteriochlorophyll molecules and Q A in Ϸ200 ps and then to Q B in 20-100 s. Q A acts as a one-electron acceptor only, whereas Q B plays the role of a two-electron gate and can accept two protons before leaving the RC.The crystal structure of the RCs of the two species of photosynthetic bacteria that have been investigated the most, namely Rhodobacter sphaeroides and Rhodopseudomonas viridis, has been solved in several laboratories (2-9). The best atomic resolution for which structural data on the Q A binding sites are presently available is 2.65 Å for the former species and 2.3 Å for the latter. For these two highly homologous proteins, the structural models reveal that the bonding interactions of Q A , which are 2-methyl-3-nonaprenyl-1,4-naphthoquinone (menaquinone-9) in Rp. viridis and 2,3-dimethoxy-5-methyl-6-decaprenyl-1,4-benzoquinone (ubiquinone-10) in Rb. sphaeroides, are relatively well defined (within the Ϯ0.25-to 0.5-Å precision on the position of the nonhydrogen atoms in the x-ray data), although the details vary among the various structures. Notably, the identity of some of the residues involved in hydrogen bonding and the relative strength of the hydrogen bonds to the two carbonyls of Q A are still not totally clear (2-9).The precise knowledge of the interac...

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Section: Discussionmentioning

confidence: 72%

“…A similar signal appears at 1,346(ϩ)͞1,342(Ϫ) cm Ϫ1 in the Q A Ϫ ͞Q A spectrum of Rb. sphaeroides reconstituted with 2,3-dimethyl-1,4-naphthoquinone (17,31). This signal probably corresponds to the upshift upon Q A reduction of the C 2 OCH 3 mode of vitamin K 1 absorbing at 1,330 cm Ϫ1 in vitro (Fig.…”

Section: Discussionmentioning

confidence: 86%

Efficient exchange of the primary quinone acceptor Q _A in isolated reaction centers of Rhodopseudomonas viridis

Breton

1997

Proc. Natl. Acad. Sci. U.S.A.

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“…Recently, the interest in characterizing the environment and bonding pattern of the RC quinones in their neutral and anionic states has triggered investigation by several FTIR spectroscopy approaches: replacement with modified or isotopically-labelled quinones [9]; comparison of P " QA -/PQA and P + QU -/PQn spectra either by steady-state [9- [7,14]. In the present study, we report that addition of reductants and mediators, which rapidly reduce P + , makes possible the photochemical generation of pure QB -/Qn FTIR difference spectra on isolated bacterial RCs.…”

Section: Discussionmentioning

confidence: 99%

Probing the secondary quinone (Q_B) environment in photosynthetic bacterial reaction centers by light‐induced FTIR difference spectroscopy

Breton¹,

Berthomieu²,

Thibodeau³

et al. 1991

FEBS Letters

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The photoreduction of the secondary electron aeeeptor, QB, has been characterized by light-induced Fourier transform infrared differenc~ spectroscopy of tlb. sphaeroides and Rp. viridis reaction centers, The reaction ~ntcrs were supplemented with ubiquinon¢ (UQto or UQ0). The Qastate was generated either by continuous illumination at very low intensity or by single flash in the presence of rexiox compounds which rapidly reduce the photooxidized primary electron donor P+. This approach yields spectra free from P and P* contributions making possible the study of the microenvironment of Qn and Qa-. Assignments are proposed for the C:_u.O vibration of Qa-and tentatively for the C =O and C=C vibrations of Qa.

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“…Compared to the DAD/ascorbate mixture used in several rapid-scan FTIR studies [13,22,23] the ferrocyanide/TMPD mix provides a series of advantages: (i) faster P 870 + reduction; (ii) shorter relaxation time between measuring cycles; (iii) the possibility of performing measures at lower temperature (down to 260 K [21]). The main drawback comes from the presence in the spectra of strong contributions from TMPD redox changes (the main positive bands are at 1545 and 1382 cm −1 due to TMPD ox ; a strong negative band at 1520 cm −1 is due to TMPD red ) [9]. The first trace in Fig.…”

Section: Resultsmentioning

confidence: 99%

Rapid-scan FTIR difference spectroscopy applied to ubiquinone reduction in photosynthetic reaction centers: Role of redox mediators

Mezzetti

2010

Spectroscopy

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Abstract. Rapid-scan FTIR difference spectroscopy was used to investigate light-induced reduction of the ubiquinone Q B , and the oxidation kinetics of Q B − and QH 2 by external mediators in isolated reaction centers (RCs) from R. sphaeroides. As redox mediators, a Ferrocyanide/N,N,N ,N -tetramethyl-p-phenylenediamine (TMPD) mixture and an Ascorbate/2,3,5,6-tetramethylp-phenylenediamine (DAD) mixture are compared.Results show that TMPD red rapidly reduces the photoproduced P 870 + primary donor. The process is fast enough to record rapid-scan FTIR spectra devoid of P 870 + bands down to 260 K. Results show also that TMPD ox oxidises both Q B − and QH 2 faster than DAD ox . In particular, Q B − is oxidised faster than QH 2 at all temperatures studied.Results are discussed in the framework of time-resolved infrared studies on R. sphaeroides RCs, showing advantages/drawbacks of the proposed experimental approach.

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Light-Induced Charge Separation in Photosynthetic Bacterial Reaction Centers Monitored by FTIR Difference Spectroscopy: the QA Vibrations

Cited by 14 publications

References 10 publications

Efficient exchange of the primary quinone acceptor Q _A in isolated reaction centers of Rhodopseudomonas viridis

Efficient exchange of the primary quinone acceptor Q _A in isolated reaction centers of Rhodopseudomonas viridis

Probing the secondary quinone (Q_B) environment in photosynthetic bacterial reaction centers by light‐induced FTIR difference spectroscopy

Rapid-scan FTIR difference spectroscopy applied to ubiquinone reduction in photosynthetic reaction centers: Role of redox mediators

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Light-Induced Charge Separation in Photosynthetic Bacterial Reaction Centers Monitored by FTIR Difference Spectroscopy: the QA Vibrations

Cited by 14 publications

References 10 publications

Efficient exchange of the primary quinone acceptor Q A in isolated reaction centers of Rhodopseudomonas viridis

Efficient exchange of the primary quinone acceptor Q A in isolated reaction centers of Rhodopseudomonas viridis

Probing the secondary quinone (QB) environment in photosynthetic bacterial reaction centers by light‐induced FTIR difference spectroscopy

Rapid-scan FTIR difference spectroscopy applied to ubiquinone reduction in photosynthetic reaction centers: Role of redox mediators

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Efficient exchange of the primary quinone acceptor Q _A in isolated reaction centers of Rhodopseudomonas viridis

Efficient exchange of the primary quinone acceptor Q _A in isolated reaction centers of Rhodopseudomonas viridis

Probing the secondary quinone (Q_B) environment in photosynthetic bacterial reaction centers by light‐induced FTIR difference spectroscopy