Structure and function of bacterial photosynthetic reaction centres

Fehér, G.; Allen, James P.; Okamura, M. Y.; Rees, Douglas C.

doi:10.1038/339111a0

Cited by 812 publications

(735 citation statements)

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“…The SADS of the two excited states and three radical pair states involved in this scheme were consistent with what is known about the spectra of these states. However, whether or not five components with different spectra were absolutely needed for an adequate description of the data could not be decided, because the differences in the SADS for radical pair states (P + H L -) 1 and (P + H L -) 2 were not large enough to identify these as discrete components with sufficient certainty. Decreasing the number of components used in the global analysis from five to four (one of these being a multi-exponential decay) reduced the quality of the fit to the experimental data, causing a 7% increase in the weighted rms error.…”

Section: Implications Of Our Findings For the Mechanism Of Primary Chmentioning

confidence: 99%

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Primary Electron Transfer Kinetics in Membrane-Bound Rhodobacter sphaeroides Reaction Centers: A Global and Target Analysis

et al. 1997

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Absorbance difference kinetics were measured on quinone-reduced membrane-bound wild type Rhodobacter sphaeroides reaction centers in the wavelength region from 690 to 1060 nm using 800 nm excitation. Global analysis of the data revealed five lifetimes of 0.18, 1.9, 5.1, and 22 ps and a long-lived component for the processes that underlie the spectral evolution of the system. The 0.18 ps component was ascribed to energy transfer from the excited state of the accessory bacteriochlorophyll (B*) to the primary donor (P*). The 1.9 ps component was associated with a state involving a BChl anion absorbing in the 1020 nm region. This led to the conclusion that primary electron transfer is best described by a model in which the electron is passed from P* to the acceptor bacteriopheophytin (H L ) via the monomeric bacteriochlorophyll (B L ), with the formation of the radical pair state P + B L-. An analysis assuming partial direct charge separation from B* [Van Brederode, M. E., Jones, M. R., and Chem. Phys. Lett. 268,[143][144][145][146][147][148][149] was also consistent with the data. Within the framework of a five component model, the 5.1 and 22 ps lifetimes were associated with charge separation and relaxation of the P + H L -radical pair state respectively, providing a description which adequately accounted for the complex kinetics of decay of P*. Alternatively, by assuming that the 5.1 and 22 ps components originate from a single component with a multi-exponential decay, a simpler analysis with only four components could be employed, resulting in only a small increase (7%) in the weighted root mean square error of the fit. In both descriptions part of the decay of P* proceeds with a lifetime of about 2 ps. The relative merits of these alternative descriptions of the primary events in light-driven electron transfer are discussed. Similar measurements on YM210H mutant reaction centers revealed four lifetimes of 0.2, 3.1, and 12 ps and a long-lived component. The 3.1 and 12 ps lifetimes are ascribed to multi-exponential decay of the P* state. The differences with the WT data are discussed.The reaction center (RC) of purple bacteria is responsible for the conversion of light energy into a transmembrane electrical potential. The structures of the RC from two species of purple bacteria, Rhodopseudomonas (Rps.) Viridis and Rhodobacter (Rb.) sphaeroides, have been solved to high resolution (1, 2). They reveal an assembly of protein subunits and redox cofactors that are arranged around an axis of approximate 2-fold symmetry. The primary donor of electrons (P) is a pair of excitonically-coupled bacteriochloropyll a (BChl) molecules positioned close to the periplasmic face of the protein. The remaining redox cofactors, two monomeric BChls (B), two molecules of bacteriopheophytin a (H), and two ubiquinones (Q), are arranged around the symmetry axis in two branches that span the membrane dielectric. Excitation of P initiates a sequence of electron transfer reactions that result in the separation of charge across the ...

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Section: Implications Of Our Findings For the Mechanism Of Primary Chmentioning

confidence: 99%

“…Viridis and Rhodobacter (Rb.) sphaeroides, have been solved to high resolution (1,2). They reveal an assembly of protein subunits and redox cofactors that are arranged around an axis of approximate 2-fold symmetry.…”

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Primary Electron Transfer Kinetics in Membrane-Bound Rhodobacter sphaeroides Reaction Centers: A Global and Target Analysis

et al. 1997

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“…14,15 Each subunit accommodates two light harvesting BChl a molecules giving rise to an absorption band at 875 nm. The reaction center complex accommodates a BChl a dimer (special pair, primary donor, P), two accessory BChl a molecules (B A , B B ), two bacteriopheophytin a (BPheo a) molecules (H A , H B ), and two ubiquinones (Q A , Q B ) bound to two protein subunits denoted L and M. The cofactors are arranged in two nearly identical branches, called A and B, which share the primary donor, P. 9,11,16,17 In particular the RC from Rhodobacter (Rb.) sphaeroides has served as a cornerstone for elucidating structure−function relationships employing a large variety of spin resonance 18−23 and optical spectroscopies.…”

Section: ■ Introductionmentioning

confidence: 99%

The Open, the Closed, and the Empty: Time-Resolved Fluorescence Spectroscopy and Computational Analysis of RC-LH1 Complexes from Rhodopseudomonas palustris

et al. 2015

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ABSTRACT:We studied the time-resolved fluorescence of isolated RC-LH1 complexes from Rhodopseudomonas palustris as a function of the photon fluence and the repetition rate of the excitation laser. Both parameters were varied systematically over 3 orders of magnitude. On the basis of a microstate description we developed a quantitative model for RC-LH1 and obtained very good agreement between experiments and elaborate simulations based on a global master equation approach. The model allows us to predict the relative population of RC-LH1 complexes with the special pair in the neutral state or in the oxidized state P + and those complexes that lack a reaction center. ■ INTRODUCTIONPhotosynthetic purple bacteria have evolved a wonderful modular principle for the light-harvesting (LH) apparatus that captures the solar radiation. These modules consist of pairs of hydrophobic, low molecular weight polypeptides that noncovalently bind a small number of bacteriochlorophyll (Bchl a) and carotenoid (Car) molecules and that self-assemble to produce the native pigment−protein complexes. 1−6 Most purple bacteria have two main types of complexes, the core complex, RC-LH1, and the peripheral complex, LH2. In the photosynthetic membrane the LH2 complexes are arranged in a two-dimensional network around the perimeter of the RC-LH1 complexes and the light energy absorbed by LH2 is transferred via LH1 to the reaction center (RC) where it is used to separate charge across the membrane. 7 For many years, high-resolution structural information has been available for the RC, 8−11 and the peripheral light-harvesting complexes 1−3 for a couple of species, whereas the first higher-resolution X-ray structure for a RC-LH1 complex has been determined only recently. 6 The current view is that there are at least two distinct classes of RC-LH1 complexes: Those that are monomeric, i.e., consisting of one RC surrounded by one LH1 complex, and those that are dimeric. 12,13 For RC-LH1 from Rps. palustris exists a lowresolution X-ray structure. 4 Accordingly, the RC is enclosed by an overall elliptically shaped LH1 consisting of 15 αβ-subunits that feature a gap, which is also consistent with data from optical single-molecule experiments. 14,15 Each subunit accommodates two light harvesting BChl a molecules giving rise to an absorption band at 875 nm. The reaction center complex accommodates a BChl a dimer (special pair, primary donor, P), two accessory BChl a molecules (B A , B B ), two bacteriopheophytin a (BPheo a) molecules (H A , H B ), and two ubiquinones (Q A , Q B ) bound to two protein subunits denoted L and M. The cofactors are arranged in two nearly identical branches, called A and B, which share the primary donor, P. 9,11,16,17 In particular the RC from Rhodobacter (Rb.) sphaeroides has served as a cornerstone for elucidating structure−function relationships employing a large variety of spin resonance 18−23 and optical spectroscopies. 24−31 From these studies it is well established that in the RC the absorbed photon-energy is used to dri...

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“…Those enzymes on which there is a wealth of structural information include Rubisco (Curmi et al, 1992 ;Newman & Gutteridge, 1993 ;Taylor & Andersson, 1997) and the H-protein (Pares et al, 1994 ;Macherel et al, 1996) of the glycine decarboxylase complex involved in photorespiration in C $ plants, such as pea, in which it accounts for 30-50 % of total mitochondrial protein. Similarly, the robustness and high levels of expression of the reaction-centre complexes in photosynthetic bacteria and their associated lightharvesting complexes have enabled their structures to be determined to high resolution by X-ray crystallography (Fenna & Matthews, 1975 ;Deisenhofer et al, 1984 ;Allen et al, 1987 ;Feher et al, 1989 ;McDermott et al, 1995 ;Koepke et al, 1996). These advances have provided the stimulus for parallel structural studies on PSI and PSII from higher plants (see below), which are again feasible as the result of the abundance and relative stability of these photosynthetic units.…”

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Tansley Review No. 109.

Cogdell

Lindsay

2000

New Phytologist

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This review sets out the case that now is the time for plant science to establish the technologies required for routinely studying the structure and function of plant proteins. The impact that protein structural information can have is illustrated here with reference to photosynthesis. Our understanding of the precise molecular mechanisms of the light-reactions of photosynthesis has been transformed by the combination of high-resolution protein structural data and detailed functional studies. The past few years have been a particularly exciting time to be engaged in basic plant science research. The application of modern techniques of molecular biology has allowed many key questions to be addressed. The stage is now set for an even bigger revolution as the current plant genome sequencing projects are completed. If these advances are going to be fully exploited, plant science must get to grips with studying proteins, not just genes. Reliable methods for the overexpression of proteins in their native state coupled with routine access to structure determination must become the norm rather than the exception. In 1998 there were about 9000 protein structures deposited in the Brookhaven database. Very few of these are plant proteins. This trend will have to be reversed if research in molecular plant science is to fulfil its potential.

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Structure and function of bacterial photosynthetic reaction centres

Cited by 812 publications

References 74 publications

Primary Electron Transfer Kinetics in Membrane-Bound Rhodobacter sphaeroides Reaction Centers: A Global and Target Analysis

Primary Electron Transfer Kinetics in Membrane-Bound Rhodobacter sphaeroides Reaction Centers: A Global and Target Analysis

The Open, the Closed, and the Empty: Time-Resolved Fluorescence Spectroscopy and Computational Analysis of RC-LH1 Complexes from Rhodopseudomonas palustris

Tansley Review No. 109.

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