Specific alteration of the oxidation potential of the electron donor in reaction centers from Rhodobacter sphaeroides.

Lin, Xiaomei; Murchison, H. A.; Nagarajan, V.; Parson, Walther; Allen, James P.; Williams, Joann

doi:10.1073/pnas.91.22.10265

Cited by 272 publications

(381 citation statements)

References 30 publications

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“…Such a conclusion has been made on the basis of spectrophotometric measurements of DA related to reversible photooxidation of the primary electron donor, P. As in the case with ferrocyanide (a known exogenous electron donor to P C ), Mn 2C in the presence of bicarbonate accelerated the re-reduction of P C . The midpoint potential for the P C /P of anoxygenic purple bacteria is 0.45-0.50 V (Prince et al 1976;Klimov et al 1977;Lin et al 1994) and a similar E m is found in our work for the pair P C /P in RCs isolated from Rh. iodosum.…”

Section: Discussionsupporting

confidence: 89%

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Redox interaction of Mn–bicarbonate complexes with reaction centres of purple bacteria

Khorobrykh

Terentyev

Zharmukhamedov

et al. 2007

Phil. Trans. R. Soc. B

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It is found that dark reduction of photooxidized primary electron donor P 870 C in reaction centres from purple anoxygenic bacteria (two non-sulphur Fe-oxidizing Rhodovulum iodosum and Rhodovulum robiginosum, Rhodobacter sphaeroides R-26 and sulphur alkaliphilic Thiorhodospira sibirica) is accelerated upon the addition of Mn 2C jointly with bicarbonate (30-75 mM). The effect is not observed if Mn 2C and HCO 3 K have been replaced by Mg 2C and HCO 2 K , respectively. The dependence of the effect on bicarbonate concentration suggests that formation of Mn 2C -bicarbonate complexes, Mn(HCO 3 ) C and/or Mn(HCO 3 ) 2 , is required for re-reduction of P 870 C with Mn 2C . The results are considered as experimental evidence for a hypothesis on possible participation of Mnbicarbonate complexes in the evolutionary origin of oxygenic photosynthesis in the Archean era.

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Section: Discussionsupporting

confidence: 89%

“…robiginosum and Th. sibirica was found to be equal to 450G30 mV (which is close to E m of P in other purple bacteria; Prince et al 1976;Klimov et al 1977;Lin et al 1994).…”

Section: Resultssupporting

confidence: 53%

Redox interaction of Mn–bicarbonate complexes with reaction centres of purple bacteria

Khorobrykh

Terentyev

Zharmukhamedov

et al. 2007

Phil. Trans. R. Soc. B

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“…We assume k in , to a first approximation, to be independent of the mutation. This assumption is supported by the observations of Lin et al (80), who have reported only a weak dependence of the rate of charge recombination between Q A -and P870 + on the reduction potential of P870 + /P870. Any increase of k in with E′ P + /P would if anything lead to an underestimate of K zp .…”

Section: Redox and Kinetic Properties Of Mutationssupporting

confidence: 74%

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

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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.

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“…The wild-type RCs were isolated from a deletion strain complemented with the wild-type genes (6). Cells were grown semiaerobically under nonphotosynthetic conditions, and RCs were isolated after published conditions by using lauryl dimethylamine oxide (Fluka) as previously described (7). Crystals were grown with sizes up to 10 mm in length by using conditions similar to those described by Ermler and coworkers (8).…”

Section: Methodsmentioning

confidence: 99%

Interactions between lipids and bacterial reaction centers determined by protein crystallography

Cámara-Artigas

Brune

Allen

2002

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

136

118

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The structure of the reaction center from Rhodobacter sphaeroides has been solved by using x-ray diffraction at a 2.55-Å resolution limit. Three lipid molecules that lie on the surface of the protein are resolved in the electron density maps. In addition to a cardiolipin that has previously been reported [McAuley, K. E., Fyfe, P. K., Ridge, J. P., Isaacs, N. W., Cogdell, R. J. & Jones, M. R. (1999) Proc. Natl. Acad. Sci. USA 96, 14706 -14711], two other major lipids of the cell membrane are found, a phosphatidylcholine and a glucosylgalactosyl diacylglycerol. The presence of these three lipids has been confirmed by laser mass spectroscopy. The lipids are located in the hydrophobic region of the protein surface and interact predominately with hydrophobic amino acids, in particular aromatic residues. Although the cardiolipin is over 15 Å from the cofactors, the other two lipids are in close contact with the cofactors and may contribute to the difference in energetics for the two branches of cofactors that is primarily responsible for the asymmetry of electron transfer. The glycolipid is 3.5 Å from the active bacteriochlorophyll monomer and shields this cofactor from the solvent in contrast to a much greater exposed surface evident for the inactive bacteriochlorophyll monomer. The phosphate atom of phosphatidylcholine is 6.5 Å from the inactive bacteriopheophytin, and the associated electrostatic interactions may contribute to electron transfer rates involving this cofactor. Overall, the lipids span a distance of Ϸ30 Å, which is consistent with a bilayer-like arrangement suggesting the presence of an ''inner shell'' of lipids around membrane proteins that is critical for membrane function.I ntegral membrane proteins are found in the cell membrane surrounded by lipids. The biophysical and biochemical properties of these proteins are critically determined by the lipid environment. The lipid composition of cell membranes is complex, containing a variety of phospholipids, glycolipids, and other small molecules. In the purple nonsulfur bacterium Rhodobacter sphaeroides, the major lipids are the phospholipids, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin, or diphosphatidyl glycerol, and two glycolipids, sulfoquinovosyl diacylglycerol and glucosylgalactosyl diacylglycerol (1). The relative amounts of these lipids vary significantly depending on specific growth conditions, in particular the oxygen level, although the fatty acid chains are always predominately 18:1 with only minor contributions from 18:0, 16:0, and 16:1 and trace amounts of smaller chains. The lipid composition is known to critically determine the morphology of the cell membrane, but whether the lipids can affect the photosynthetic energy conversion processes remains an outstanding question.Understanding the influence of the lipid properties on the photosynthetic complexes, or any other integral membrane proteins, is in most cases limited by the lack of detailed structural information concerning membrane proteins. To ...

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Specific alteration of the oxidation potential of the electron donor in reaction centers from Rhodobacter sphaeroides.

Cited by 272 publications

References 30 publications

Redox interaction of Mn–bicarbonate complexes with reaction centres of purple bacteria

Redox interaction of Mn–bicarbonate complexes with reaction centres of purple bacteria

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

Interactions between lipids and bacterial reaction centers determined by protein crystallography

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