Orientation of chromophores in reaction centers of Rhodopseudomonas sphaeroides: A photoselection study

Vermeglio, A.; Breton, Jacques; Paillotin, Guy; Cogdell, Richard J.

doi:10.1016/0005-2728(78)90118-4

Cited by 97 publications

(35 citation statements)

References 17 publications

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“…6); the negative lobe of the CD spectrum splits into a constant and a variable component. The former, located at about 812 nm, is assigned to the upper exciton band, in agreement with previous indirect assignments by Vermeglio et al (1978). If our assignment is correct, the large negative and positive CD bands that shift with the absorptions must be derived from the monomeric (modified) pigments.…”

Section: Hugo Scheer/andreas Strucksupporting

confidence: 71%

“…Due to triplet interaction, a distinetion seems possible, however, after reconstitution with carotenoids and triplet spectroscopy of the latter (G. Hartwich, V. Aust, A. Angerhofer, H. Scheer, unpublished results). The Bphes at HA and HB can be distinguished by their Qx absorptions around 535 nm; the former absorbs at longer wavelengths (Clayton and Yamamoto, 1976;Vermeglio et al, 1978;Breton, 1985;Kirmaier et al, 1985;Tiede et al, 1985). The two bands overlap at room temperature but can be deconvoluted; at low temperatures they are well resolved.…”

Section: Spectroscopic Methodsmentioning

confidence: 99%

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Bacterial Reaction Centers with Modified Tetrapyrrole Chromophores

Scheer¹,

Struck

1993

Photosynthetic Reaction Center

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II. Norris, James R., Date. QP517.P45P46 1993 '3342-dc20 92-43633This book is printed on acid-free paper.© Academic Press, Inc. References 78 Genetic Analysis of Photosynthetic Membrane Biogenesis in Rhodobacter sphaeroides I. IntroductionSeveral different methods are available for preparing reaction centers with nonnative chromophores: (1) (re)assembly from the Polypeptides, pigments, and other components such as quinones, iron, and possibly others; (2) exchange of chromophores into native or partly denatured reaction centers; (3) modification of chromophores in native or partly denatured reaction centers by chemical or enzymatic means; (4) modification of binding sites to incorporate different chromophores, for example, by mutagenesis, and (5) mutagenic modifications of the pigments biosynthetic pathways. With the exception of the last one, all these approaches have been used on different Complete reconstitution of the complexes (Method 1) from the isolated constituent Polypeptides and suitably modified pigments is likely to have the greatest potential, but to date has been impossible with reaction centers. This technique has been applied successfully to the core light-harvesting complexes (LHCI) of purple bacteria (Miller et al, 1987;Ghosh et al, 1988;Parkes-Loach et al, 1988 Chang et al, 1990a,b;Heller and Loach, 1990) and to the peripheral light-harvesting chromoprotein LHCII-ß of higher plants (Plumley and Schmidt, 1987). The method has been extended by Paulsen etat. (1990Paulsen etat. ( ,1991 to the full-length and modified LHCII-ß precursor Polypeptides expressed in and isolated from Escherichia coli and by Schmidt et al. (1991) to other green plant peripheral light-harvesting complexes.Site-directed mutagenesis of the binding pockets (Method 4) has been used extensively to exchange bacteriochlorophylls (Behls) with their metalfree derivatives, for example, bacteriopheophytins (Bphes) and vice versa in reaction centers (RCs) from Rhodobacter (Rb.) capsulatus and Rb. sphaeroides (Table I)-With only a Single exception, whenever the histidine(s) ligating the central magnesium atom(s) of the Bchl(s) were replaced by hydrophobic amino acids, stably assembled RCs were obtained in which the Behls at the respective site(s) were replaced by Bphe to yield stably assembled and isolatable RCs (Bylina and Youvan, 1988; Coleman and Youvan, 1990;Robles et al, 1990;Schenck et al, 1990;Woodbury et al, 1990). In reversing this reaction, replacement of leucine or isoleucine next to the central N-4 cavity of Bphe with histidine resulted in binding of Behl at the respective site. Some results are available with amino acid residues of intermediate ligation strength. Serine or threonine selected binding of Behl at BA and BB (Bylina et al, 1990); glutamine (mutants H-L173Q and H-M200Q 2 ) at the sites of the special pair resulted in binding of Behl also (Bylina and Youvan, 1988). Omission of Bphe HL was found in a mutant of Rb. capsulatus in which part of the D helix of subunit L was replaced by the symmetrically equiv...

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Section: Hugo Scheer/andreas Strucksupporting

confidence: 71%

Section: Spectroscopic Methodsmentioning

confidence: 99%

Bacterial Reaction Centers with Modified Tetrapyrrole Chromophores

Scheer¹,

Struck

1993

Photosynthetic Reaction Center

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“…Theory of LD-ADMR. The theoretical description of LD-ADMR is analogous to that of photoselection (9). A necessary condition for accurate results is that the sample is initially truly random-i.e., one has to extrapolate to zero intensity of the exciting microwave field.…”

Section: Methodsmentioning

confidence: 99%

Exciton interactions in reaction centers of the photosynthetic bacterium Rhodopseudomonas viridis probed by optical triplet-minus-singlet polarization spectroscopy at 1.2 K monitored through absorbance-detected magnetic resonance

Lous

Hoff

1987

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

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Linear dichroic triplet-minus-singlet [LD-(T -S)] spectra of isolated reaction centers of the photosynthetic bacterium Rhodopseudomonas viridis have been measured at 1.2 K with the linear dichroic absorbance-detected magnetic resonance (LD-ADMR) technique for two mutually perpendicular directions of the preferred axis. The LD-(T -S) spectra have been calibrated with respect to the corresponding (T -S) spectra as a function of applied microwave power and quantitatively interpreted using the formalism of photoselection. The transition moment of the optical transition at 1007 nm makes angles of 72°± 50 and 15°± 50 with the triplet x and y spin axes, respectively. The experimental spectra have been simulated employing exciton theory and using the atomic coordinates of the resolved crystal structure of the reaction center. The spectral interpretation yields the angles between the transition moments of the various absorption bands of the (T -S) spectra and the triplet axes, and between the moments themselves, with the triplet state of the primary donor 3P localized on the P-bacteriochlorophyll b in the "active" (L) chain.Following the elucidation of the crystal structure of the reaction center (RC) of the photosynthetic bacterium Rhodopseudomonas (Rps.) viridis at atomic resolution (1, 2), attention has been focused on the interpretation by exciton theory of its optical properties, including the absorption spectrum, the linear and circular dichroic spectra, and the absorption difference spectrum (oxidized-minus-reduced) (3)(4)(5). Especially the absorption difference spectrum of the RC in the triplet state and in the singlet ground state is of interest, as the triplet state of the primary donor, 3P, perturbs the RC much less than the charged oxidized state that determines the commonly studied oxidized-minus-reduced difference spectrum.In this communication we report on the measurement of accurate, highly resolved triplet-minus-singlet (T -S) and linear dichroic LD-(T -S) absorption difference spectra of isolated RC of Rps. viridis, using absorbance-detected magnetic resonance (ADMR and LD-ADMR) (6, 7). The LD-ADMR technique permits the recording of calibrated LD-(T -S) spectra with respect to two mutually perpendicular axes (7,8), yielding for the 1007-nm absorption band angles of 720 + 50 and 150 ± 50 with the triplet x and y spin axes, respectively.From a spectral analysis based on exciton theory the angles between the various optical transition moments are de- described (6). Samples were slowly frozen in the dark after addition of 10 mM sodium ascorbate and 67% (vol/vol) ethylene glycol.The ADMR and LD-ADMR techniques are described in refs. 6 and 7, respectively. The LD-(T -S) spectrum presents the difference between the (T -S)II and the (T -S)L spectra, where 11 and I refer to parallel and perpendicular to the magnetic field vector of a polarized microwave field, respectively.The two ADMR resonance frequencies, 358.5 and 597.4MHz, correspond to the IDI -Ej and the IDI + JEl transitions, where D and E are ...

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“…The preparation of RCs containing the modified [3-vinyl]-132-hydroxy-BChl-a shows a substantially different absorption spectrum from native RC ( This shoulder is due to an incomplete exchange (80%o) of the monomeric BChl-a. Part of this shoulder may also be due to the upper excitonic component of the Q(P) band (22,25,26).…”

Section: P+b P+h-p+q- This Model Ismentioning

confidence: 99%

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

Finkele

Lauterwasser

Struck

et al. 1992

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

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The primary electron transfer has been investigated by femtosecond time-resolved absorption spectroscopy in two chemically modified reaction centers (RC) of Rhodobacter sphaeroides, in which the monomeric bacteriochlorophylls BA and BB have both been exchanged by 132-hydroxybacteriochlorophyll a or [3-vinylJ-132-hydroxybac-teriochlorophyll a. The kinetics of the primary electron transfer are not influenced by the 132-hydroxy modification. In RCs containing [3-vinyl]-132-hydroxybacteriochlorophyll a the primary rate is reduced by a factor of 10. HThe three known x-ray structures of bacterial reaction centers (RCs) show basically the same arrangement of the cofactors (see refs. 1-4). They form two branches [A (active) and B (inactive)], which are arranged in an approximate twofold symmetry. Surprisingly, the electron transfer (ET) has been found to proceed exclusively along the A branch (5-7). From the primary donor, P870 or P960, an electron is transferred to the acceptor quinone (QA) The structural arrangement of the chromophores suggests an ET via the two intervening pigments-i.e., the monomeric bacteriochlorophyll (BChl) BA and the bacteriopheophytin (BPhe) HAWhile there is general agreement that the BPhe HA is an intermediate electron acceptor (5-9), the role of the BChl BA located between the BChl dimer P and the BPhe HA is still controversially discussed. First studies with sufficient time resolution and an appropriate excitation wavelength led to the conclusion that the state P+B-(P, primary donor) is not a real intermediate in the ET (5,10,11). However, a direct ET from P* to HA over an edge-to-edge distance of '10 A can be accounted for only by a "superexchange" transfer via a virtual intermediate P+B-(12-15 Kinetic measurements were performed at T 298 K in cuvettes of 1-mm path length under stirring. The sample volume was 0.2-0.3 ml. The transmission was between T 10%o and 50% at A = 860 nm (80-25 ,uM The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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Orientation of chromophores in reaction centers of Rhodopseudomonas sphaeroides: A photoselection study

Cited by 97 publications

References 17 publications

Bacterial Reaction Centers with Modified Tetrapyrrole Chromophores

Bacterial Reaction Centers with Modified Tetrapyrrole Chromophores

Exciton interactions in reaction centers of the photosynthetic bacterium Rhodopseudomonas viridis probed by optical triplet-minus-singlet polarization spectroscopy at 1.2 K monitored through absorbance-detected magnetic resonance

Primary electron transfer kinetics in bacterial reaction centers with modified bacteriochlorophylls at the monomeric sites BA,B.

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