Fourier transform infrared spectroscopy of special pair bacteriochlorophylls in homodimeric reaction centers of heliobacteria and green sulfur bacteria

Noguchi, Takumi

doi:10.1007/s11120-009-9509-0

Cited by 12 publications

(26 citation statements)

References 59 publications

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“…The corresponding residues in GbRC and HbRC are the non-H-bonding residues PscA-Val689 and PshA-Met602, respectively ( Fig. 1B ); this observation is consistent with previous spectroscopic observations that the 13 1 -keto C=O groups in P840 and P800 are free from H-bonding 21 26 29 . In addition, each of the 2 axial His ligands in P700 (PsaA-His680 and PsaB-His661) seems to interact with a nearby threonine residue (PsaA-Thr742 and PsaB-Thr727, respectively) through an H-bond to the main chain amide C=O (PsaA-Phe676 and PsaB-Phe656) ( Fig.…”

Section: Resultssupporting

confidence: 92%

“…In contrast, the P800 + /P800 FTIR difference spectrum for HbRC showed a single positive 13 1 -keto C=O signal; this observation suggests that the positive charge is significantly delocalized over the BChl g dimer on the IR timescale 21 25 . Another prominent feature of the P800 + /P800 difference spectrum was a differential signal arising from the S-H stretching vibration of an H-bonded cysteine side chain 21 25 . PshA-Cys601, which was predicted to be located near the histidine ligand of P800, was proposed to be responsible for this S-H signal.…”

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confidence: 88%

“…One of the factors determining the E m of the special pair is the charge distribution on a (B)Chl dimer 20 ; this distribution is determined by the symmetry of the dimer, as well as its protein environment. However, whether the structures and reactions of the homodimeric RCs are truly symmetric is still unknown 3 21 . Asymmetry could be introduced by the assembly of 2 identical RC polypeptides in an asymmetrical way or the asymmetrical binding of peripheral subunits such as membrane-bound cytochrome c (cyt c z in green sulfur bacteria) and the F A /F B protein.…”

mentioning

confidence: 99%

“…Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been used to study the homodimeric GbRC and HbRC to investigate the molecular interactions of the special pairs at the atomic level 21 22 23 24 25 26 . The P840 + /P840 FTIR difference spectrum for GbRC showed 2 prominent bands for P840 + ; these bands were assigned to the 13 1 -keto C=O stretching vibrations of constituent BChl a molecules 21 26 , and their presence implied that there is an asymmetric charge distribution, at least on the infrared (IR) timescale determined by the uncertainty principle (i.e., subpicsecond). In contrast, the P800 + /P800 FTIR difference spectrum for HbRC showed a single positive 13 1 -keto C=O signal; this observation suggests that the positive charge is significantly delocalized over the BChl g dimer on the IR timescale 21 25 .…”

mentioning

confidence: 99%

“…The P840 + /P840 FTIR difference spectrum for GbRC showed 2 prominent bands for P840 + ; these bands were assigned to the 13 1 -keto C=O stretching vibrations of constituent BChl a molecules 21 26 , and their presence implied that there is an asymmetric charge distribution, at least on the infrared (IR) timescale determined by the uncertainty principle (i.e., subpicsecond). In contrast, the P800 + /P800 FTIR difference spectrum for HbRC showed a single positive 13 1 -keto C=O signal; this observation suggests that the positive charge is significantly delocalized over the BChl g dimer on the IR timescale 21 25 . Another prominent feature of the P800 + /P800 difference spectrum was a differential signal arising from the S-H stretching vibration of an H-bonded cysteine side chain 21 25 .…”

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confidence: 99%

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

Azai

Sano

Kato

et al. 2016

Sci Rep

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Homodimeric photosynthetic reaction centers (RCs) in green sulfur bacteria and heliobacteria are functional homologs of Photosystem (PS) I in oxygenic phototrophs. They show unique features in their electron transfer reactions; however, detailed structural information has not been available so far. We mutated PscA-Leu688 and PscA-Val689 to cysteine residues in the green sulfur bacterium Chlorobaculum tepidum; these residues were predicted to interact with the special pair P840, based on sequence comparison with PS I. Spectroelectrochemical measurements showed that the L688C and V689C mutations altered a near-infrared difference spectrum upon P840 oxidation, as well as the redox potential of P840. Light-induced Fourier transform infrared difference measurements showed that the L688C mutation induced a differential signal of the S-H stretching vibration in the P840+/P840 spectrum, as reported in P800+/P800 difference spectrum in a heliobacterial RC. Spectral changes in the 131-keto C=O region, caused by both mutations, revealed corresponding changes in the electronic structure of P840 and in the hydrogen-bonding interaction at the 131-keto C=O group. These results suggest that there is a common spatial configuration around the special pair sites among type 1 RCs. The data also provided evidence that P840 has a symmetric electronic structure, as expected from a homodimeric RC.

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Section: Resultssupporting

confidence: 92%

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confidence: 88%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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

Azai

Sano

Kato

et al. 2016

Sci Rep

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Ubiquinol formation in isolated photosynthetic reaction centres monitored by time-resolved differential FTIR in combination with 2D correlation spectroscopy and multivariate curve resolution

et al. 2010

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Two-dimensional correlation analysis was carried out in combination with multivariate curve resolution-alternating least squares (MCR-ALS) to analyse time-resolved infrared (IR) difference spectra probing photoinduced ubiquinol formation in detergent-isolated reaction centres from Rhodobacter sphaeroides. The dynamic 2D IR correlation spectra have not only allowed the determination of the concomitance or non-concomitance of different chemical events through known marker bands but also have helped identify new vibrational bands related to the complex series of photochemical and redox reactions. In particular, a strong positive band located at 1565 cm⁻¹ was found to be synchronous with the process of ubiquinol formation. In addition, a tailored MCR-ALS analysis was performed using a priori chemical knowledge of the system, in particular including the pure spectrum of one species obtained from an external measurement. Enhancing the MCR-ALS performance in this way in time-dependent processes is relevant, especially when other essential pieces of information, such as kinetic models, are unavailable. The results give evidence of four independent spectral contributions. Three of them show marker bands for a monoelectronic reduction of the primary quinone QA (QA⁻/QA transition, first contribution), for a monoelectronic reduction of a secondary quinone QB (QB⁻/QB transition, second contribution) and for ubiquinol formation (third contribution). The results obtained also confirm that a key rate-limiting factor is the slow ubiquinone and ubiquinol exchange among micelles, which strongly influences the kinetic profiles of the involved species.

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Time-resolved infrared spectroscopy in the study of photosynthetic systems

Mezzetti

Leibl

2016

Photosynth Res

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Time-resolved (TR) infrared (IR) spectroscopy in the nanosecond to second timescale has been extensively used, in the last 30 years, in the study of photosynthetic systems. Interesting results have also been obtained at lower time resolution (minutes or even hours). In this review, we first describe the used techniques-dispersive IR, laser diode IR, rapid-scan Fourier transform (FT)IR, step-scan FTIR-underlying the advantages and disadvantages of each of them. Then, the main TR-IR results obtained so far in the investigation of photosynthetic reactions (in reaction centers, in light-harvesting systems, but also in entire membranes or even in living organisms) are presented. Finally, after the general conclusions, the perspectives in the field of TR-IR applied to photosynthesis are described.

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Fourier transform infrared spectroscopy of special pair bacteriochlorophylls in homodimeric reaction centers of heliobacteria and green sulfur bacteria

Cited by 12 publications

References 59 publications

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

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

Ubiquinol formation in isolated photosynthetic reaction centres monitored by time-resolved differential FTIR in combination with 2D correlation spectroscopy and multivariate curve resolution

Time-resolved infrared spectroscopy in the study of photosynthetic systems

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