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Okamura M. George Feher: a pioneer in reaction center research. PHOTOSYNTHESIS RESEARCH 2014; 120:29-42. [PMID: 24104959 DOI: 10.1007/s11120-013-9927-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 09/16/2013] [Indexed: 06/02/2023]
Abstract
Our understanding of photosynthesis has been greatly advanced by the elucidation of the structure and function of the reaction center (RC), the membrane protein responsible for the initial light-induced charge separation in photosynthetic bacteria and green plants. Although today we know a great deal about the details of the primary processes in photosynthesis, little was known in the early days. George Feher made pioneering contributions to photosynthesis research in characterizing RCs from photosynthetic bacteria following the ground-breaking work of Lou Duysens and Rod Clayton (see articles in this issue by van Gorkom and Wraight). The work in his laboratory at the University of California, San Diego, started in the late 1960s and continued for over 30 years. He isolated a pure RC protein and used magnetic resonance spectroscopy to study the primary reactants. Following this pioneering work, Feher studied the detailed structure of the RC and the basic electron and proton transfer functions that it performs using a wide variety of biophysical and biochemical techniques. These studies, together with work from many other researchers, have led to our present detailed understanding of these proteins and their function in photosynthesis. The present article is a brief historical account of his pioneering contributions to photosynthesis research. A more detailed description of his work can be found in an earlier biographical paper (Feher in Photosynth Res 55:1-40, 1998a).
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Affiliation(s)
- Melvin Okamura
- Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0354, USA,
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Worland ST, Yamagishi A, Isaacs S, Sauer K, Hearst JE. Labeling quinone-binding sites in photosynthetic reaction centers: A 38-kilodalton protein associated with the acceptor side of photosystem II. Proc Natl Acad Sci U S A 2010; 84:1774-8. [PMID: 16593817 PMCID: PMC304523 DOI: 10.1073/pnas.84.7.1774] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
2-Acetoxymethyl-1,4-naphthoquinone (2-AcOMeNQ) binds with rapid kinetics and high affinity to the primary quinone Q(A) site of reaction centers from Rhodopseudomonas capsulata. Binding of 2-AcOMeNQ fully restores electron-transfer activity with kinetics that is similar, but not identical, to that seen with ubiquinone-50. When bound at the Q(A) site, 2-AcOMeNQ preferentially labels the L subunit. This preference suggests that 2-AcOMeNQ labels primarily the region of a quinone-binding site that is close to the first isoprenoid unit of the side chain, which is expected from the location and structure of the reaction region of the molecule. In photosystem II particles from Synechococcus sp., 2-AcOMeNQ primarily labels two polypeptides with apparent molecular masses of 38 and 19 kDa. Labeling of only the 38-kDa polypeptide is sufficiently sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) to conclude that it is involved in binding quinones on the acceptor side of photosystem II. Although we have not yet identified the 38-kDa protein, its properties suggest that it is the D2 protein. From the DCMU-sensitive labeling and from homologies to functionally important regions of the bacterial reaction-center subunits, we propose that the 38-kDa protein is intimately involved in binding the cofactors that mediate primary photochemistry.
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Affiliation(s)
- S T Worland
- Department of Chemistry and Laboratory of Chemical Biodynamics, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
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Brown AE, Gilbert CW, Guy R, Arntzen CJ. Triazine herbicide resistance in the photosynthetic bacterium Rhodopseudomonas sphaeroides. Proc Natl Acad Sci U S A 2010; 81:6310-4. [PMID: 16593520 PMCID: PMC391913 DOI: 10.1073/pnas.81.20.6310] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The photoaffinity herbicide azidoatrazine (2-azido-4-ethylamino-6-isopropylamino-s-triazine) selectively labels the L subunit of the reaction center of the photosynthetic bacterium Rhodopseudomonas sphaeroides. Herbicide-resistant mutants retain the L subunit and have altered binding properties for methylthio- and chloro-substituted triazines as well as altered equilibrium constants for electron transfer between primary and secondary electron acceptors. We suggest that a subtle alteration in the L subunit is responsible for herbicide resistance and that the L subunit is the functional analog of the 32-kDa Q(B) protein of chloroplast membranes.
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Affiliation(s)
- A E Brown
- Department of Botany and Microbiology, Auburn University, Auburn, AL 36849
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Williams JC, Steiner LA, Ogden RC, Simon MI, Feher G. Primary structure of the M subunit of the reaction center from Rhodopseudomonas sphaeroides. Proc Natl Acad Sci U S A 2010; 80:6505-9. [PMID: 16593385 PMCID: PMC390381 DOI: 10.1073/pnas.80.21.6505] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reaction center is a membrane-bound bacteriochlorophyll-protein complex that mediates the primary photochemical events in the photosynthetic bacterium Rhodopseudomonas sphaeroides. The previously determined amino-terminal sequences of the three subunits of the reaction center protein were used to design synthetic mixed oligonucleotide probes for the structural genes encoding the subunits. One of these probes was used to isolate and clone a fragment of DNA from R. sphaeroides that contained the gene encoding the M subunit. The nucleotide sequence of this gene was determined by the dideoxy method. In addition, a number of tryptic and chymotryptic peptides from the M protein were isolated and subjected to sequence analysis, and the sequence of the carboxyl terminus was determined. Together with the amino-terminal sequence, the data establish the primary structure of the M protein. The distribution of hydrophobic residues in the amino acid sequence suggests the presence of five membrane-spanning segments. A significant homology was found between the amino acid sequence of the M subunit and a thylakoid membrane protein (M(r) 32,000) from spinach that has been implicated in herbicide and quinone binding.
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Affiliation(s)
- J C Williams
- Department of Biology, University of California, San Diego, La Jolla, CA 92093
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Gong X, Xie T, Yu L, Hesterberg M, Scheide D, Friedrich T, Yu CA. The ubiquinone-binding site in NADH:ubiquinone oxidoreductase from Escherichia coli. J Biol Chem 2003; 278:25731-7. [PMID: 12730198 DOI: 10.1074/jbc.m302361200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An azido-ubiquinone derivative, 3-azido-2-methyl-5-methoxy[3H]-6-decyl-1,4-benzoquinone ([3H]azido-Q), was used to study the ubiquinone/protein interaction and to identify the ubiquinone-binding site in Escherichia coli NADH:ubiquinone oxidoreductase (complex I). The purified complex I showed no loss of activity after incubation with a 20-fold molar excess of [3H]azido-Q in the dark. Illumination of the incubated sample with long wavelength UV light for 10 min at 0 degrees C caused a 40% decrease of NADH:ubiquinone oxidoreductase activity. SDS-PAGE of the complex labeled with [3H]azido-Q followed by analysis of the radioactivity distribution among the subunits revealed that subunit NuoM was heavily labeled, suggesting that this protein houses the Q-binding site. When the [3H]azido-Q-labeled NuoM was purified from the labeled reductase by means of preparative SDS-PAGE, a 3-azido-2-methyl-5-methoxy-6-decyl-1,4-benzoquinone-linked peptide, with a retention time of 41.4 min, was obtained by high performance liquid chromatography of the protease K digest of the labeled subunit. This peptide had a partial NH2-terminal amino acid sequence of NH2-VMLIAILALV-, which corresponds to amino acid residues 184-193 of NuoM. The secondary structure prediction of NuoM using the Toppred hydropathy analysis showed that the Q-binding peptide overlaps with a proposed Q-binding motif located in the middle of the transmembrane helix 5 toward the cytoplasmic side of the membrane. Using the PHDhtm hydropathy plot, the labeled peptide is located in the transmembrane helix 4 toward the periplasmic side of the membrane.
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Affiliation(s)
- Xing Gong
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078, USA
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Feher G. My road to biophysics: picking flowers on the way to photosynthesis. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2002; 31:1-44. [PMID: 11988461 DOI: 10.1146/annurev.biophys.31.082901.134147] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- George Feher
- Department of Physics, University of California-San Diego, La Jolla, CA 92037, USA.
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Probing the smallest functional unit of the reaction center ofRhodospirillum rubrumG-9 with proteinases. FEBS Lett 2001. [DOI: 10.1016/0014-5793(84)80063-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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QA
-depletion and reconstitution of a reaction center preparation from the photosynthetic bacterium Rhodopseudomonas viridis. FEBS Lett 2001. [DOI: 10.1016/0014-5793(90)81192-q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Giménez-Gallego G, Suanzes P, Ramírez JM. Functional bacterial photoreaction centres with only one type of protein. FEBS Lett 2001. [DOI: 10.1016/0014-5793(82)81071-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Iwaki M, Takahashi M, Shimada K, Takahashi Y, Itoh S. Photoaffinity labeling of the phylloquinone-binding polypeptides by 2-azidoanthraquinone in photosystem I particles. FEBS Lett 1992; 312:27-30. [PMID: 1426233 DOI: 10.1016/0014-5793(92)81403-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A photoaffinity label, 2-azido-9,10-anthraquinone, binds at the quinone-binding (Q phi) site with high affinity and can substitute for the secondary acceptor, phylloquinone, in photosystem I reaction center of spinach. Phylloquinone-depleted photosystem I particles reconstituted with azido[3H]anthraquinone were illuminated with UV light and analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The large core polypeptides (psaA and/or psaB) were selectively labeled. The labeling was competitively inhibited in the presence of anthraquinone. These results indicate that the Q phi site is located on psaA or psaB polypeptides.
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Affiliation(s)
- M Iwaki
- Division of Bioenergetics, National Institute for Basic Biology, Okazaki, Japan
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Liu BL, Yang LH, Hoff AJ. On the depletion and reconstitution of both QA and metal in reaction centers of the photosynthetic bacterium Rb. sphaeroides R-26. PHOTOSYNTHESIS RESEARCH 1991; 28:51-58. [PMID: 24414858 DOI: 10.1007/bf00033714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/1991] [Accepted: 03/25/1991] [Indexed: 06/03/2023]
Abstract
Four possible ways to prepare QA-depleted, Fe-depleted and QA-reconstituted RCs were studied: (1) first depleting the Fe, then depleting QA and finally reconstituting QA (D-Fe, D-Q, R-Q), (2) first depleting QA, then depleting the Fe and finally reconstituting QA (D-Q, D-Fe, R-Q), (3) first depleting QA, then reconstituting QA and finally depleting Fe (D-Q, R-Q, D-Fe), (4) first depleting QA, then depleting the Fe and reconstituting QA in the same step (D-Q, D-Fe-R-Q). Our results showed that: method (1) results in the irreversible loss of photochemical activity; method (2) and (3) result in low recovery of the photochemical activity and poor yield of Fe-depleted, QA-reconstituted RCs; method (4) gives surprisingly good results. This method allows for the first time to prepare the QA-depleted, Fe-depleted, QA-reconstituted RCs with high recovery of the photochemical activity and good yield. The sample has 98% of photochemical activity (yield of P(+) QA (-)) compared with that of the native RCs and shows strong polarization of the EPR signal of QA (-) under continuous illumination at 5K. The decay halftime of I(-) is slow (∼5 ns) compared with that of the native RCs, but it is the same as that measured for the RCs from which only iron is removed. These results indicate that the depletion of iron and the reconstitution of QA have been successful. Reconstitution of the QA-depleted, Fe-depleted and QA-reconstituted RCs with Zn(2+) gives also the spin-polarized QA (-), and yields the same decay of I(-) (halftime 200 ps) as that of the native RCs.
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Affiliation(s)
- B L Liu
- Department of Biophysics, Huygens Laboratory, State University of Leiden, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
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Allen JP, Feher G, Yeates TO, Komiya H, Rees DC. Structure of the reaction center from Rhodobacter sphaeroides R-26: the cofactors. Proc Natl Acad Sci U S A 1987; 84:5730-4. [PMID: 3303032 PMCID: PMC298936 DOI: 10.1073/pnas.84.16.5730] [Citation(s) in RCA: 564] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The three-dimensional structure of the cofactors of the reaction center of Rhodobacter sphaeroides R-26 has been determined by x-ray diffraction and refined at a resolution of 2.8 A with an R value of 26%. The main features of the structure are similar to the ones determined for Rhodopseudomonas viridis [Michel, H., Epp, O. & Deisenhofer, J. (1986) EMBO J. 5, 2445-2451]. The cofactors are arranged along two branches, which are approximately related to each other by a 2-fold symmetry axis. The structure is well suited to produce light-induced charge separation across the membrane. Most of the structural features predicted from physical and biochemical measurements are confirmed by the x-ray structure.
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Yu L, Yang FD, Yu CA. Interaction and identification of ubiquinone-binding proteins in ubiquinol-cytochrome c reductase by azido-ubiquinone derivatives. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(20)71194-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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de Vitry C, Wollman FA, Delepelaire P. Function of the polypeptides of the photosystem II reaction center in Chlamydomonas reinhardtii. Localization of the primary reactants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1984. [DOI: 10.1016/0005-2728(84)90039-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Rochaix JD, Dron M, Rahire M, Malnoe P. Sequence homology between the 32K dalton and the D2 chloroplast membrane polypeptides of Chlamydomonas reinhardii. PLANT MOLECULAR BIOLOGY 1984; 3:363-370. [PMID: 24310569 DOI: 10.1007/bf00033383] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/1984] [Revised: 04/16/1984] [Accepted: 04/20/1984] [Indexed: 06/02/2023]
Abstract
The region of the chloroplast genome of Chlamydomonas reinhardii containing the gene of the thylakoid polypeptide D2 (psbD) has been sequenced. A unique open reading frame of 350 codons exists in this region. Because the first ATG is followed 11 codons downstream by a second one, the D2 polypeptide consists of either 339 or 350 amino acids. Comparison of the sequences of D2 and the 32K dalton polypeptides, both of which are associated with photosystem II, reveals partial homology. Although, the overall homology of these two polypeptides is only 27%, they contain several related regions and their hydropathic profiles are strikingly similar. These data suggest that the two polypeptides may have related functions and/or that their genes may have originated from a common ancestor. Alternatively, convergent evolution of these polypeptides may be due to structural constraints in the thylakoid membrane. Limited sequence homology is also observed between the D2 polypeptide and some of the subunits of the reaction centers of photosynthetic bacteria.
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Affiliation(s)
- J D Rochaix
- Department of Molecular Biology, University of Geneva, 1211, Geneva 4, Switzerland
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Alt J, Morris J, Westhoff P, Herrmann RG. Nucleotide sequence of the clustered genes for the 44 kd chlorophyll a apoprotein and the ?32 kd?-like protein of the photosystem II reaction center in the spinach plastid chromosome. Curr Genet 1984; 8:597-606. [DOI: 10.1007/bf00395705] [Citation(s) in RCA: 188] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/1984] [Indexed: 11/29/2022]
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Kleinfeld D, Okamura MY, Feher G. Electron transfer in reaction centers of Rhodopseudomonas sphaeroides. I. Determination of the charge recombination pathway of D+QAQ(-)B and free energy and kinetic relations between Q(-)AQB and QAQ(-)B. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 766:126-40. [PMID: 6331502 DOI: 10.1016/0005-2728(84)90224-x] [Citation(s) in RCA: 205] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The electron-transfer reactions and thermodynamic equilibria involving the quinone acceptor complex in bacterial reaction centers from R. sphaeroides were investigated. The reactions are described by the scheme: (Formula: see text). We found that the charge recombination pathway of D+QAQ(-)B proceeds via the intermediate state D+Q(-)AQB, the direct pathway contributing less than approx. 5% to the observed recombination rate. The method used to obtain this result was based on a comparison of the kinetics predicted for the indirect pathway (given by the product kAD-times the fraction of reaction centers in the Q-AQB state) with the observed recombination rate, kobsD+----D. The kinetic measurements were used to obtain the pH dependence (6.1 smaller than or equal to pH smaller than or equal to 11.7) of the free energy difference between the states Q(-)AQB and QAQ(-)B. At low pH (less than 9) QAQ(-)B is stabilized relative to Q(-)AQB by 67 meV, whereas at high pH Q(-)AQB is energetically favored. Both Q(-)A and Q(-)B associate with a proton, with pK values of 9.8 and 11.3, respectively. The stronger interaction of the proton with Q(-)B provides the driving force for the forward electron transfer.
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Stein RR, Castellvi AL, Bogacz JP, Wraight CA. Herbicide-quinone competition in the acceptor complex of photosynthetic reaction centers from Rhodopseudomonas sphaeroides: a bacterial model for PS-II-herbicide activity in plants. J Cell Biochem 1984; 24:243-59. [PMID: 6376526 DOI: 10.1002/jcb.240240306] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A select group of herbicides that inhibit photosystem II also act at the acceptor side of the reaction center (RC) from the photosynthetic bacterium Rhodopseudomonas sphaeroides, with much the same relative specificity as in plants. These include the triazines and some phenolic compounds. The proposal that herbicides inhibit the electron transfer from the primary quinone (QA) to the secondary quinone (QB) by competing for the secondary quinone binding site--the B-site--[5], is tested here with terbutryn, the most potent of the triazines. Competition between terbutryn and ubiquinone (Q-10) was observed using the kinetics of the back-reaction as a measure of inhibition. The model includes binding equilibria before and after flash activation. The binding constants for the preflash (dark) equilibria, for reaction centers in 0.14% lauryl dimethylamine-N-oxide (LDAO), were KDi = 0.8 microM terbutryn, KDq = 2 microM Q-10; both are detergent-concentration dependent. After flash activation, binding equilibrium is not fully restored on the time scale of the back-reaction because terbutryn unbinds slowly. This gives rise to biphasic decay kinetics from which koff for terbutryn was estimated to be 3 sec-1. Titrations of the rate of the slow back reaction indicated that the post-flash equilibrium is less sensitive to inhibitor, in a manner that is independent of the much stronger binding of the semiquinone, Q-B, and indicative of a direct effect of the redox state of QA on the affinity of the B-site for ligands. However, the effects on KLi and KDq could not be separated: either KLi greater than KDi or KLq less than KDq. Some triazine-resistant mutants have been isolated and are described. All appear to be herbicide binding site mutants. Whole cells and photosynthetic membrane vesicles (chromatophores) exhibit a 10-50-fold increase in resistance to triazines due, in large part, to an increase in the rate of unbinding (koff). The modifications of the binding site appear to diminish the affinity of the B-site for ubiquinone as well as terbutryn. It is concluded that bacterial RCs are a useful model for the study of herbicide activity and specificity.
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Agalidis I, Reiss-Husson F. Several properties of the LM unit extracted with sodium dodecyl sulfate from Rhodopseudomonas sphaeroides purified reaction centers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1983. [DOI: 10.1016/0005-2728(83)90093-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Debus R, Valkirs G, Okamura M, Feher G. Localization of the secondary quinone-binding site in reaction centers from Rhodopseudomonas sphaeroides R-26 by antibody inhibition of electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1982. [DOI: 10.1016/0005-2728(82)90067-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Valkirs GE, Feher G. Topography of reaction center subunits in the membrane of the photosynthetic bacterium, rhodopseudomonas sphaeroides. J Cell Biol 1982; 95:179-88. [PMID: 6754742 PMCID: PMC2112351 DOI: 10.1083/jcb.95.1.179] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The localization of the reaction center polypeptides (L, M, and H) in the membranes of both the wild-type, strain 2.4.1, and the carotenoidless mutant, R-26, of Rhodopseudomonas sphaeroides was determined by using affinity-purified antibodies specific for these proteins. Binding of the antibodies to reaction center subunits in spheroplasts was visualized in the electron microscope by immunoferritin labeling. The H and M subunits were labeled at both the cytoplasmic and the periplasmic surfaces of the membrane, whereas the L subunit was labeled only at the periplasmic surface of the membrane. Thus, the reaction center is asymmetrically oriented in the membrane with at least two subunits (H and M) spanning the membrane.
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Photooxidation of the Reaction Center Chlorophylls and Structural Properties of Photosynthetic Reaction Centers. ACTA ACUST UNITED AC 1982. [DOI: 10.1007/978-3-642-81795-3_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
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BACCARINI-MELANDRI A, CASADIO R, MELANDRI B. Electron Transfer, Proton Translocation, and ATP Synthesis in Bacterial Chromatophores. CURRENT TOPICS IN BIOENERGETICS 1981. [DOI: 10.1016/b978-0-12-152512-5.50010-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Odermatt E, Snozzi M, Bachofen R. Labeling of chromatophore membranes and reaction centers from the photosynthetic bacterium Rhodospirillum rubrum with the hydrophobic marker 5-[125I]iodonaphthyl-1-azide.. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 591:372-80. [PMID: 7397129 DOI: 10.1016/0005-2728(80)90168-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Chromatophores of the photosynthetic bacterium Rhodospirillum rubrum and isolated reaction centers were labeled with the lipophilic membrane marker 5-[125I]iodonaphthyl-1-azide. The two smaller reaction center proteins L and M bind more label than the larger subunit H, a fact supporting the proposed localisation of the 3 subunits obtained with hydrophilic labels. Besides these integral proteins the lipids, among them mainly the pigments and the quinones, are highly labeled suggesting a hydrophobic environment around these molecules and a preferred reactivity to iodonaphthylazide. Such a hydrophobic environment may be of great importance for the function of the photosynthetic reaction centers especially for the charge separation and the primary reactions in electron transport.
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