Comparative Study of Reaction Centers from Photosynthetic Purple Bacteria: Electron Paramagnetic Resonance and Electron Nuclear Double Resonance Spectroscopy

Rautter, J.; Lendzian, Friedhelm; Lubitz, Wolfgang; Wang, S.; Allen, James P.

doi:10.1021/bi00206a010

Cited by 86 publications

(100 citation statements)

References 27 publications

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“…ENDOR-ENDOR measurements were performed on a Bruker ESP 300E X-band EPR spectrometer with home-built ENDOR accessories (29). ENDOR experiments were carried out on the cation radical P700 ϩ⅐ of PS I complexes in frozen solution at 150 K as described earlier (17).…”

Section: Methodsmentioning

confidence: 99%

Species-specific Differences of the Spectroscopic Properties of P700

Witt

Bordignon

Carbonera

et al. 2003

Journal of Biological Chemistry

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We applied optical spectroscopy, magnetic resonance techniques, and redox titrations to investigate the properties of the primary electron donor P700 in photosystem I (PS I) core complexes from cyanobacteria (Thermosynechococcus elongatus, Spirulina platensis, and Synechocystis sp. PCC 6803), algae (Chlamydomonas reinhardtii CC2696), and higher plants (Spinacia oleracea). Remarkable species-specific differences of the optical properties of P700 were revealed monitoring the ( 3 P700 -P700) and (P700 ؉⅐ -P700) absorbance and CD difference spectra. The main bleaching band in the Q y region differs in peak position and line width for the various species. In cyanobacteria the absorbance of P700 extends more to the red compared with algae and higher plants which is favorable for energy transfer from red core antenna chlorophylls to P700 in cyanobacteria. The amino acids in the environment of P700 are highly conserved with two distinct deviations. In C. reinhardtii a Tyr is found at position PsaB659 instead of a Trp present in all other organisms, whereas in Synechocystis a Phe is found instead of a Trp at the homologous position PsaA679. We constructed several mutants in C. reinhardtii CC2696. Strikingly, no PS I could be detected in the mutant YW B659 indicating steric constraints unique to this organism. In the mutants WA A679 and YA B659 significant changes of the spectral features in the ( 3 P700 -P700), the (P700 ؉⅐ -P700) absorbance difference and in the (P700 ؉⅐ -P700) CD difference spectra are induced. The results indicate structural differences among PS I from higher plants, algae, and cyanobacteria and give further insight into specific protein-cofactor interactions contributing to the optical spectra.

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Section: Methodsmentioning

confidence: 99%

Species-specific Differences of the Spectroscopic Properties of P700

Witt

Bordignon

Carbonera

et al. 2003

Journal of Biological Chemistry

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“…EPR, ENDOR, and electron-nuclear-nuclear triple resonance (special TRIPLE) spectra were recorded with a Bruker ESP 300E spectrometer (Billerica, MA) as described (23), using ENDOR accessories and an ENDOR TM110 cavity of local design (24). The cation radical of the BChl dimer was generated in the cavity by continuous wave illumination with a tungsten halogen lamp (100 W, 700-950 nm using filters) (23). The hfcs were determined by fits of the spectra (25), and the spin density distribution was calculated from the ratios of the methyl hfcs assigned to each half of the dimer as described below.…”

Section: Methodsmentioning

confidence: 99%

Relationship between the oxidation potential and electron spin density of the primary electron donor in reaction centers from Rhodobacter sphaeroides

Artz

Williams

Allen

et al. 1997

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

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124

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The primary electron donor in bacterial reaction centers is a dimer of bacteriochlorophyll a molecules, labeled L or M based on their proximity to the symmetryrelated protein subunits. The electronic structure of the bacteriochlorophyll dimer was probed by introducing small systematic variations in the bacteriochlorophyll-protein interactions by a series of site-directed mutations that replaced residue Leu M160 with histidine, tyrosine, glutamic acid, glutamine, aspartic acid, asparagine, lysine, and serine. The midpoint potentials for oxidation of the dimer in the mutants showed an almost continuous increase up to Ϸ60 mV compared with wild type. The spin density distribution of the unpaired electron in the cation radical state of the dimer was determined by electron-nuclear-nuclear triple resonance spectroscopy in solution. The ratio of the spin density on the L side of the dimer to the M side varied from Ϸ2:1 to Ϸ5:1 in the mutants compared with Ϸ2:1 for wild type. The correlation between the midpoint potential and spin density distribution was described using a simple molecular orbital model, in which the major effect of the mutations is assumed to be a change in the energy of the M half of the dimer, providing estimates for the coupling and energy levels of the orbitals in the dimer. These results demonstrate that the midpoint potential can be fine-tuned by electrostatic interactions with amino acids near the dimer and show that the properties of the electronic structure of a donor or acceptor in a protein complex can be directly related to functional properties such as the oxidation-reduction midpoint potential.The reaction center is the site of the primary process in photosynthesis, which is the conversion of light energy into a charge-separated state (for reviews, see ref. 1). The electron transfer process in the reaction center has the remarkable aspect that the quantum yield is near unity, that is, for every photon absorbed, one electron is transferred. The reaction center isolated from the purple bacterium Rhodobacter sphaeroides is particularly useful for the study of electron transfer because this complex has been well characterized biochemically and spectroscopically, and the three-dimensional structure has been determined by x-ray diffraction (2-5). The reaction center has two core subunits, L and M, that form the binding sites for the cofactors and are related by an Ϸ2-fold symmetry axis. The primary electron donor (P) consists of two symmetry-related bacteriochlorophyll (BChl) a molecules labeled P L and P M that overlap at the ring I position and are separated by Ϸ3.5 Å (Fig. 1). Light absorption causes the excitation of P, and within 3.5 ps, an electron is transferred to a bacteriopheophytin acceptor. Electron transfer proceeds to the primary quinone acceptor, Q A , in Ϸ200 ps and to the secondary quinone, Q B , in Ϸ200 s. After reduction of the donor by cytochrome c 2 , absorption of a second photon leads to the transfer of a second electron to Q B , which then leaves the protein carry...

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“…The two spectra show some very small but distinct differences of the proton hfcs. Based upon previous studies, the shifts are unlikely to arise from a difference in the carotenoid composition, due to incorporation of spheroidene and spheroidenone in cultures grown under anaerobic and aerobic conditions, respectively, or differences in the preparations (Geßner et al 1992;Rautter et al 1994). The ENDOR/TRIPLE spectrum is sensitive to electrostatic interactions as indicated by the large changes observed upon introduction of hydrogen bonds or use of zwitterionic detergents (Rautter et al 1995;Müh et al 1998;.…”

Section: X-band Epr Measurementsmentioning

confidence: 94%

“…by mapping the spin density distribution over the conjugated system. In wild type, the distribution is asymmetric with more of the spin density being located on the L-side of P (P L ) than the M-side (P M ) (Geßner et al 1992;Lendzian et al 1993;Rautter et al 1994;1995;Artz et al 1997;Müh et al 2002;Lubitz et al 2002). Due to the large number of protons in the BChl macrocycle (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…(c) Molecular structure of bacteriochlorophyll a (BChl a) with IUPAC numbering; the two methyl groups 2 1 and 12 1 and the b-protons 7, 8, 17, and 18 are indicated studies of P •? in RCs both in liquid solution and single crystals, several hfcs have been resolved and unambiguously assigned (Geßner et al 1992;Lendzian et al 1993;Artz et al 1997;Rautter et al 1994;1995;Müh et al 2002). In general, for samples in liquid solutions, the technique of Special TRIPLE is well suited to obtain highquality spectra that can be used to gain detailed insight into the spin and charge distribution within P •?…”

Section: Introductionmentioning

confidence: 99%

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EPR, ENDOR, and Special TRIPLE measurements of P•+ in wild type and modified reaction centers from Rb. sphaeroides

et al. 2008

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The influence of the protein environment on the primary electron donor, P, a bacteriochlorophyll a dimer, of reaction centers from Rhodobacter sphaeroides, has been investigated using electron paramagnetic resonance and electron nuclear double resonance spectroscopy. These techniques were used to probe the effects on P that are due to alteration of three amino acid residues, His L168, Asn L170, and Asn M199. The introduction of Glu at L168, Asp at L170, or Asp at M199 changes the oxidation/ reduction midpoint potential of P in a pH-dependent manner (Williams et al. (2001) Biochemistry 40, 15403-15407). For the double mutant His L168 to Glu and Asn at L170 to Asp, excitation results in electron transfer along the A-side branch of cofactors at pH 7.2, but at pH 9.5, a long-lived state involving B-side cofactors is produced (Haffa et al. (2004) J Phys Chem B 108, 4-7). Using electron paramagnetic resonance spectroscopy, the mutants with alterations of each of the three individual residues and a double mutant, with changes at L168 and L170, were found to have increased linewidths of 10.1-11.0 G compared to the linewidth of 9.6 G for wild type. The Special TRIPLE spectra were pH dependent, and at pH 8, the introduction of aspartate at L170 increased the spin density ratio, q L /q M , to 6.1 while an aspartate at the symmetry related position, M199, decreased the ratio to 0.7 compared to the value of 2.1 for wild type. These results indicate that the energy of the two halves of P changes by about 100 meV due to the mutations and are consistent with the interpretation that electrostatic interactions involving these amino acid residues contribute to the switch in pathway of electron transfer.

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Comparative Study of Reaction Centers from Photosynthetic Purple Bacteria: Electron Paramagnetic Resonance and Electron Nuclear Double Resonance Spectroscopy

Cited by 86 publications

References 27 publications

Species-specific Differences of the Spectroscopic Properties of P700

Species-specific Differences of the Spectroscopic Properties of P700

Relationship between the oxidation potential and electron spin density of the primary electron donor in reaction centers from Rhodobacter sphaeroides

EPR, ENDOR, and Special TRIPLE measurements of P•+ in wild type and modified reaction centers from Rb. sphaeroides

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