Structural homology of reaction centers from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis as determined by x-ray diffraction.

Allen, James P.; Fehér, G.; Yeates, Todd O.; Rees, DC; Deisenhofer, Johann; Michel, Hartmut; Huber, Robert

doi:10.1073/pnas.83.22.8589

Cited by 347 publications

(172 citation statements)

References 26 publications

Supporting

Mentioning

165

Contrasting

Unclassified

Order By: Relevance

“…This observation is consistent with the estimated 10 Å center to center distance between the metal centers of these chlorophylls from electron and X-ray diffraction studies of PSII crystals (17,18,73) as opposed to the 7.6 Å found in bacterial reaction centers (3)(4)(5).…”

Section: Location Of 3 P As a Function Of Temperaturesupporting

confidence: 88%

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

et al. 2001

View full text Add to dashboard Cite

Site-directed mutations were introduced to replace D1-His198 and D2-His197 of the D1 and D2 polypeptides, respectively, of the photosystem II (PSII) reaction center of Synechocystis PCC 6803. These residues coordinate chlorophylls P A and P B which are homologous to the special pair Bchlorophylls of the bacterial reaction centers that are coordinated respectively by histidines L-173 and M-200 (202). P A and P B together serve as the primary electron donor, P, in purple bacterial reaction centers. In PS II, the site-directed mutations at D1 His198 affect the P + -P-absorbance difference spectrum. The bleaching maximum in the Soret region (in WT at 433 nm) is blue-shifted by as much as 3 nm. In the D1 His198Gln mutant, a similar displacement to the blue is observed for the bleaching maximum in the Q y region (672.5 nm in WT at 80 K), whereas features attributed to a band shift centered at 681 nm are not altered. In the Y Z •-Y Z -difference spectrum, the band shift of a reaction center chlorophyll centered in WT at 433-434 nm is shifted by 2-3 nm to the blue in the D1-His198Gln mutant. The D1-His198Gln mutation has little effect on the optical difference spectrum, 3 P-1 P, of the reaction center triplet formed by P + Pheo -charge recombination (bleaching at 681-684 nm), measured at 5-80 K, but becomes visible as a pronounced shoulder at 669 nm at temperatures g150 K. Measurements of the kinetics of oxidized donor-Q A -charge recombination and of the reduction of P + by redox active tyrosine, Y Z , indicate that the reduction potential of the redox couple P + /P can be appreciably modulated both positively and negatively by ligand replacement at D1-198 but somewhat less so at D2-197. On the basis of these observations and others in the literature, we propose that the monomeric accessory chlorophyll, B A , is a long-wavelength trap located at 684 nm at 5 K. B A * initiates primary charge separation at low temperature, a function that is increasingly shared with P A * in an activated process as the temperature rises. Charge separation from B A * would be potentially very fast and form P A + B A -and/or B A + Pheo -as observed in bacterial reaction centers upon direct excitation of B A ) Proc. Natl. Acad Sci. 96, 2054-2059. The cation, generated upon primary charge separation in PSII, is stabilized at all temperatures primarily on P A , the absorbance spectrum of which is displaced to the blue by the mutations. In WT, the cation is proposed to be shared to a minor extent (∼20%) with P B , the contribution of which can be modulated up or down by mutation. The band shift at 681 nm, observed in the P + -P difference spectrum, is attributed to an electrochromic effect of P A + on neighboring B A . Because of its low-energy singlet and therefore triplet state, the reaction center triplet state is stabilized on B A at e80 K but can be shared with P A at >80 K in a thermally activated process.

show abstract

Section: Location Of 3 P As a Function Of Temperaturesupporting

confidence: 88%

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

et al. 2001

View full text Add to dashboard Cite

show abstract

“…The structures of several bacterial reaction centers have been determined (1)(2)(3)(4) and are of continuing interest due to their high degree of homology to the photosystems of higher plants (5)(6)(7). Several reviews describe the structure of the bacterial reaction center in detail (8,9).…”

mentioning

confidence: 99%

Time-resolved crystallographic studies of light-induced structural changes in the photosynthetic reaction center

Baxter

Ponomarenko

Šrajer

et al. 2004

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

View full text Add to dashboard Cite

Light-induced structural changes in the bacterial reaction center were studied by a time-resolved crystallographic experiment. Crystals of protein from Blastochloris viridis (formerly Rhodopseudomonas viridis) were reconstituted with ubiquinone and analyzed by monochromatic and Laue diffraction, in the dark and 3 ms after illuminating the crystal with a pulsed laser (630 nm, 3 mJ͞pulse, 7 ns duration). Refinement of monochromatic data shows that ubiquinone binds only in the ''proximal'' Q B binding site. No significant structural difference was observed between the light and dark datasets; in particular, no quinone motion was detected. This result may be reconciled with previous studies by postulating equilibration of the ''distal'' and ''proximal'' binding sites upon extended dark adaption, and in which movement of ubiquinone is not the conformational gate for the first electron transfer between Q A and QB.bacterial photosynthesis ͉ secondary electron transfer ͉ Laue diffraction ͉ time-resolved crystallography ͉ quinones

show abstract

“…We conclude that the excited state of the special pair has substantial charge-transfer character, and we suggest that charge separation in bacterial photosynthesis is initiated immediately upon photoexcitation of the special pair. Data for Rhodobacter sphaeroides between 340 and 1340 nm are presented and discussed in the context of the detection of chargetransfer states by Stark effect spectroscopy.The recent elucidation of the organization of the reactive components in reaction centers (RCs) from photosynthetic bacteria by x-ray diffraction (1)(2)(3)(4) makes possible an analysis of the initial charge-separation mechanism from first principles. The first step in such an analysis is the calculation of the spectroscopic properties of the RC from several species, including the absorption, circular dichroism, and linear dichroism spectra (5-9).…”

mentioning

confidence: 99%

“…The recent elucidation of the organization of the reactive components in reaction centers (RCs) from photosynthetic bacteria by x-ray diffraction (1)(2)(3)(4) makes possible an analysis of the initial charge-separation mechanism from first principles. The first step in such an analysis is the calculation of the spectroscopic properties of the RC from several species, including the absorption, circular dichroism, and linear dichroism spectra (5)(6)(7)(8)(9).…”

mentioning

confidence: 99%

Stark effect spectroscopy of Rhodobacter sphaeroides and Rhodopseudomonas viridis reaction centers

Lockhart

Boxer

1988

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

134

129

View full text Add to dashboard Cite

The nature of the initially excited state of the primary electron donor or special pair has been investigated by Stark effect spectroscopy for reaction centers from the photosynthetic bacteria Rhodopseudomonas viiis and Rhodobacter sphaeroides at 77 K. The data provide values for the magnitude of the difference in permanent dipole moment between the ground and excited state, IAuI and the angle C between ApL and the transition dipole moment for the electronic transition.IAdA and C for the lowest-energy singlet electronic transition associated with the special pair primary electron donor were found to be very similar for the two species. IA|I for this transition is substantially larger than for the Qy transitions of the monomeric pigments in the reaction center or for pure monomeric bacteriochlorophylls, for which Stark data are also reported. We conclude that the excited state of the special pair has substantial charge-transfer character, and we suggest that charge separation in bacterial photosynthesis is initiated immediately upon photoexcitation of the special pair. Data for Rhodobacter sphaeroides between 340 and 1340 nm are presented and discussed in the context of the detection of chargetransfer states by Stark effect spectroscopy.The recent elucidation of the organization of the reactive components in reaction centers (RCs) from photosynthetic bacteria by x-ray diffraction (1)(2)(3)(4) makes possible an analysis of the initial charge-separation mechanism from first principles. The first step in such an analysis is the calculation of the spectroscopic properties of the RC from several species, including the absorption, circular dichroism, and linear dichroism spectra (5-9). In a recent report we demonstrated that a quantitative analysis of the effect of an electric field on the absorption spectrum (the Stark effect spectrum) in Rhodobacter sphaeroides RCs at room temperature provides additional observables for comparison with theory (10). This work followed up on an earlier preliminary report by deLeeuv et al. (11). In the present communication we extend these measurements to a different species, Rhodopseudomonas viridis, and to low temperatures (12).Quantitative analysis of the Stark effect spectrum provides information on the magnitude of the difference in permanent dipole moment between the ground and excited state, JAput, and on the angle, (, between Ap and the transition dipole moment.Since the orientation of the transition dipole moment can be determined relative to the molecular axes from single-crystal polarized absorption measurements, the angle (can be related to the movement of charge associated with excitation of the chromophores in the RC. Stark effect data have also been obtained for monomeric photosynthetic chromophores, and this information should be useful for testing the reliability ofthe wave functions that are used for the calculation of RC spectral properties and electron transfer pathways. EXPERIMENTAL Rps. viridis RCs were prepared as previously described for Rb. sphaeroides (...

show abstract

Structural homology of reaction centers from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis as determined by x-ray diffraction.

Cited by 347 publications

References 26 publications

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

Site-Directed Mutations at D1-His198 and D2-His197 of Photosystem II in Synechocystis PCC 6803: Sites of Primary Charge Separation and Cation and Triplet Stabilization

Time-resolved crystallographic studies of light-induced structural changes in the photosynthetic reaction center

Stark effect spectroscopy of Rhodobacter sphaeroides and Rhodopseudomonas viridis reaction centers

Contact Info

Product

Resources

About