Bacterial Reaction Centers with Plant-Type Pheophytins

Scheer, Hugo; Meyer, Michaela; Katheder, Ingrid

doi:10.1007/978-1-4615-3050-3_7

Cited by 17 publications

(15 citation statements)

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“…1 a) strongly suggest that the procedure of chemical exchange described in [6] leads to a (partial) removal of BPhe molecules from the Rb. sphaeroides R-26 RCs.…”

Section: Discussionmentioning

confidence: 92%

“…In our previous work [7,8] we described room-temperature spectroscopic and photochemical properties of Rb. sphaeroides R-26 RCs chemically exchanged with pheophytin a at the bacteriopheophytin a sites HA and HB [6]. Here we report on the ability of similar preparations for electron transfer at low temperatures.…”

Section: Introductionmentioning

confidence: 83%

“…Three types of preparations were used in this work: non-treated RCs, modified and control ones. RC modification was performed according to [6]. Briefly, methanolic Phe solution was added to a 8/IM RC solution to achieve a 20-fold excess of the pigment *Corresponding author.…”

Section: Methodsmentioning

confidence: 99%

“…A promising approach to clarify this relationship is an introduction of controlled changes to the structure and the observation of consequent alterations of the RC properties. Recently a new procedure has been worked out [4][5][6], employing the chemical exchange of endogeneous pigments with those in solution. In our previous work [7,8] we described room-temperature spectroscopic and photochemical properties of Rb.…”

Section: Introductionmentioning

confidence: 99%

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Formation of charge separated state P⁺Q⁻_A and triplet state ³P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a

et al. 1994

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Low temperature optical and photochemical properties of Rhodobacter sphaeroides (R-26) reaction centers, in which bacteriopheophytin a has been replaced by plant pheophytin a, are reported. Modified reaction centers preserve the ability for photoinduced electron transfer from the primary electron donor P to the primary quinone acceptor QA at 80K. The triplet state ESR signal of modified reaction centers with prereduced QA at 10K shows an electron spin polarization pattern and ZFS parameters analogous to those for the triplet state 3p in non-treated reaction centers. It was found that at low temperature both P+QA and 3p states are formed via a precursor radical pair P+I-in which I is the introduced plant pheophytin molecule. This shows that acceptor systems of bacterial and plant (photosystem I1) reaction centers are mutually replacable in structural and functional aspects.

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“…1 a) strongly suggest that the procedure of chemical exchange described in [6] leads to a (partial) removal of BPhe molecules from the Rb. sphaeroides R-26 RCs.…”

Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Formation of charge separated state P⁺Q⁻_A and triplet state ³P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a

et al. 1994

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“…Phe a carries both changes: It is a chlorin and bears a [3-vinyl] group. For detailed information on the tested pigments and on the characterization of RC containing them at sites HA,B, readers are referred to [2,12]. These structural modifications lead to distinct spectral changes ( Fig.…”

Section: Modified Pigmentsmentioning

confidence: 99%

Probing native‐like orientation of pigments in modified reaction centers from Rhodobacter sphaeroides R26 by linear dichroism

Meyer¹,

Scheer²,

Breton

1996

FEBS Letters

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Key words: Pigment modification; Low-temperature spectroscopy; Reaction center; Asymmetry; Gel squeezing; Linear dichroism questions concerning structure-function relationships in reaction centers [4]. An important conclusion from these studies was that the monomeric BChl a at site BA is a real intermediate in the ultrafast electron transfer from P to HA [7].In all these studies, it has tacitly been assumed that the modified pigments are introduced into the binding site with the same orientation as the pigment original present and that the replacement or the treatment during exchange does not change the structure of the complex. These assumptions can be validated only by a combination of spectroscopic and structure-analytical tools. Low-temperature linear dichroism spectroscopy has been shown in the past to be a sensitive tool in this respect [8,9]. We here report linear dichroism spectra of RC in which BPhe a has been replaced with the related pigments [3-vinyl]BPhe a, [3-acetyl]Phe a, and Phe a [2], or the BChls at sites BA,B with modified ones, in order to modify their redox potentials and spectra [10].The results show all modified pigments to be arranged in the RC in the same way as the native pigments and to have no

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Bacterial Reaction Centers with Modified Tetrapyrrole Chromophores

Scheer¹,

Hartwich²

Advances in Photosynthesis and Respiration

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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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Bacterial Reaction Centers with Plant-Type Pheophytins

Abstract: The CD-ROM can be ordered through any member of the Board of Publishers orthrough NATO-PCO, Overijse, Belgium.

Cited by 17 publications

References 10 publications

Formation of charge separated state P⁺Q⁻_A and triplet state ³P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a

Formation of charge separated state P⁺Q⁻_A and triplet state ³P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a

Probing native‐like orientation of pigments in modified reaction centers from Rhodobacter sphaeroides R26 by linear dichroism

Bacterial Reaction Centers with Modified Tetrapyrrole Chromophores

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Bacterial Reaction Centers with Plant-Type Pheophytins

Abstract: The CD-ROM can be ordered through any member of the Board of Publishers orthrough NATO-PCO, Overijse, Belgium.

Cited by 17 publications

References 10 publications

Formation of charge separated state P+Q−A and triplet state 3P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a

Formation of charge separated state P+Q−A and triplet state 3P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a

Probing native‐like orientation of pigments in modified reaction centers from Rhodobacter sphaeroides R26 by linear dichroism

Bacterial Reaction Centers with Modified Tetrapyrrole Chromophores

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Formation of charge separated state P⁺Q⁻_A and triplet state ³P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a

Formation of charge separated state P⁺Q⁻_A and triplet state ³P at low temperature in Rhodobacter sphaeroides (R‐26) reaction centers in which bacteriopheophytin a is replaced by plant pheophytin a