Mutation-induced perturbation of the special pair P840 in the homodimeric reaction center in green sulfur bacteria

Azai, Chihiro; Sano, Yuko; Kato, Yuki; Noguchi, Takumi; Oh‐oka, Hirozo

doi:10.1038/srep19878

Cited by 7 publications

(11 citation statements)

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“…In contrast to heterodimers, the primary donors of homodimeric reaction centers exhibit remarkably similar midpoint potentials. Redox titrations on the primary donor, P 840 , of the GsbRC yielded a reduction potential of +217 (Azai et al, 2016)-+240 mV (Fowler et al, 1971;Prince and Olson, 1976;Hauska et al, 2001). Related experiments on P 800 from the HbRC yielded a surprisingly similar E m of +225 mV (Prince et al, 1985).…”

Section: Comparison Of the Primary Donors In Hetero And Homodimeric Reaction Centersmentioning

confidence: 87%

Shedding Light on Primary Donors in Photosynthetic Reaction Centers

et al. 2021

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Chlorophylls (Chl)s exist in a variety of flavors and are ubiquitous in both the energy and electron transfer processes of photosynthesis. The functions they perform often occur on the ultrafast (fs–ns) time scale and until recently, these have been difficult to measure in real time. Further, the complexity of the binding pockets and the resulting protein-matrix effects that alter the respective electronic properties have rendered theoretical modeling of these states difficult. Recent advances in experimental methodology, computational modeling, and emergence of new reaction center (RC) structures have renewed interest in these processes and allowed researchers to elucidate previously ambiguous functions of Chls and related pheophytins. This is complemented by a wealth of experimental data obtained from decades of prior research. Studying the electronic properties of Chl molecules has advanced our understanding of both the nature of the primary charge separation and subsequent electron transfer processes of RCs. In this review, we examine the structures of primary electron donors in Type I and Type II RCs in relation to the vast body of spectroscopic research that has been performed on them to date. Further, we present density functional theory calculations on each oxidized primary donor to study both their electronic properties and our ability to model experimental spectroscopic data. This allows us to directly compare the electronic properties of hetero- and homodimeric RCs.

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Section: Comparison Of the Primary Donors In Hetero And Homodimeric Reaction Centersmentioning

confidence: 87%

Shedding Light on Primary Donors in Photosynthetic Reaction Centers

et al. 2021

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“…The light-induced infrared difference spectrum and the comparatively low redox potential of P/P + in the HbRC and GsbRC suggest that the special pair in RC1 complexes do not exhibit H-bonding (Noguchi 2010 ; Azai et al 2016 ). Consistent with this, there is no apparent H-bonding near the 13 2 substituent of BChl g ′ of P 800 in the HbRC (Orf et al 2018a ), an observation that is especially confident due to the high resolution of the X-ray crystallographic data.…”

Section: Comparison Of the Gsbrc To Other Rcsmentioning

confidence: 99%

Recent advances in the structural diversity of reaction centers

2021

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Photosynthetic reaction centers (RC) catalyze the conversion of light to chemical energy that supports life on Earth, but they exhibit substantial diversity among different phyla. This is exemplified in a recent structure of the RC from an anoxygenic green sulfur bacterium (GsbRC) which has characteristics that may challenge the canonical view of RC classification. The GsbRC structure is analyzed and compared with other RCs, and the observations reveal important but unstudied research directions that are vital for disentangling RC evolution and diversity. Namely, (1) common themes of electron donation implicate a Ca2+ site whose role is unknown; (2) a previously unidentified lipid molecule with unclear functional significance is involved in the axial ligation of a cofactor in the electron transfer chain; (3) the GsbRC features surprising structural similarities with the distantly-related photosystem II; and (4) a structural basis for energy quenching in the GsbRC can be gleaned that exemplifies the importance of how exposure to oxygen has shaped the evolution of RCs. The analysis highlights these novel avenues of research that are critical for revealing evolutionary relationships that underpin the great diversity observed in extant RCs.

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“…The change in the hydrogen bond of the 13 1 -keto CϭO can be monitored by FTIR difference or resonance Raman spectroscopy. Indeed, for bacterial reaction centers, various sitedirected mutants changing the hydrogen bonds of the 13 1 -keto CϭO groups of bacteriochlorophylls in special pairs have been analyzed using such a spectroscopic method as well as redox potential measurement (14,(33)(34)(35), showing that hydrogen bond formation at a 13 1 -keto CϭO group increases the redox potential of a special pair. The merits of vibrational detection of the 13 1 -keto CϭO interaction are as follows.…”

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confidence: 99%

Genetically introduced hydrogen bond interactions reveal an asymmetric charge distribution on the radical cation of the special-pair chlorophyll P680

Nagao

Yamaguchi

Nakamura

et al. 2017

Journal of Biological Chemistry

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The special-pair chlorophyll (Chl) P680 in photosystem II has an extremely high redox potential ( ) to enable water oxidation in photosynthesis. Significant positive-charge localization on one of the Chl constituents, P or P, in P680 has been proposed to contribute to this high To identify the Chl molecule on which the charge is mainly localized, we genetically introduced a hydrogen bond to the 13-keto C=O group of P and P by changing the nearby D1-Val-157 and D2-Val-156 residues to His, respectively. Successful hydrogen bond formation at P and P in the obtained D1-V157H and D2-V156H mutants, respectively, was monitored by detecting 13-keto C=O vibrations in Fourier transfer infrared (FTIR) difference spectra upon oxidation of P680 and the symmetrically located redox-active tyrosines Y and Y, and they were simulated by quantum-chemical calculations. Analysis of the P680/P680 FTIR difference spectra of D1-V157H and D2-V156H showed that upon P680 formation, the 13-keto C=O frequency upshifts by a much larger extent in P (23 cm) than in P (<9 cm). In addition, thermoluminescence measurements revealed that the D1-V157H mutation increased the of P680 to a larger extent than did the D2-V156H mutation. These results, together with the previous results for the mutants of the His ligands of P and P, lead to a definite conclusion that a charge is mainly localized to P in P680^.

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Mutation-induced perturbation of the special pair P840 in the homodimeric reaction center in green sulfur bacteria

Cited by 7 publications

References 50 publications

Shedding Light on Primary Donors in Photosynthetic Reaction Centers

Shedding Light on Primary Donors in Photosynthetic Reaction Centers

Recent advances in the structural diversity of reaction centers

Genetically introduced hydrogen bond interactions reveal an asymmetric charge distribution on the radical cation of the special-pair chlorophyll P680

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