Electrometrical study of electron transfer from the terminal F<sub>A</sub>/F<sub>B</sub> iron–sulfur clusters to external acceptors in photosystem I

Mamedova, Aygun; Mamedov, Mahir D.; Gourovskaya, Kira N.; Vassiliev, Ilya R.; Golbeck, John H.; Semenov, Alexey Yu.

doi:10.1016/s0014-5793(99)01570-7

Cited by 12 publications

(5 citation statements)

References 21 publications

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“…The lack of additional electrogenicity under conditions of effective electron transfer from the F B redox center to soluble acceptors implies that this reaction is electrically silent. The finding that F A fails to donate electrons to Fld in the F B ‐deficient (HgCl 2 ‐treated) PS I complexes suggests that F B is the direct electron donor to Fld [13]. This conclusion is in line with the data obtained by monitoring the kinetics of rereduction of the photooxidized P700 in the presence of Fd and Fld [15] and the kinetics of Fd reduction [16] by control and F B ‐deficient PS I complexes.…”

Section: Electrogenic Reactions At the Acceptor Side Of Ps Isupporting

confidence: 83%

“…In a series of our works (1996–2001) [4,10–14] the direct electrometrical method was used for determining relative contributions of electron transfer reactions between Pc/cyt c 6 , the PS I complex, and Fd/Fld to the overall electrogenesis mediated by PS I. The results of our photoelectric measurements in combination with independent and virtually concurrently obtained spectroscopic data reported in [15,16] provided a new insight into the sequence of the electron transfer reactions between the terminal electron acceptors F A and F B .…”

Section: Introductionmentioning

confidence: 87%

“…Given the fact that the electron transfer reactions in the complex are essentially irreversible, the relationship for the ratio between the mean ϵ values corresponding to B→C and A→B electron transfer stages ( ϵ BC / ϵ AB ) with the photovoltage drop between B and C (ψ BC ) and between A and B (ψ AB ) can be described by the following approximate equation:

where D BC and D AB are the projections for the B→C and A→B distance vectors onto the membrane normal, respectively. Taking into account the distances between the PS I cofactors [1] and the structural model of the Fd [27] and Pc [27,28] docking sites, as well as relative contributions of the electron transfer reactions P700→A 0 and A 0 →A 1 [7], A 1 →F X [3,16], F X →F B [12], Pc→P700 [14] and F B →Fld [13] to the overall electrogenesis provided by the PS I complex, the following suggestions are made: Let the minimal value of the dielectric constant for the P700→A 0 protein region be ϵ ∼3.…”

Section: Profile Of Changes Of the Effective Dielectric Constant Alonmentioning

confidence: 99%

“…where D BC and D AB are the projections for the BCC and ACB distance vectors onto the membrane normal, respectively. Taking into account the distances between the PS I cofactors [1] and the structural model of the Fd [27] and Pc [27,28] docking sites, as well as relative contributions of the electron transfer reactions P700CA 0 and A 0 CA 1 [7], A 1 CF X [3,16], F X CF B [12], PcCP700 [14] and F B CFld [13] to the overall electrogenesis provided by the PS I complex, the following suggestions are made: 1. Let the minimal value of the dielectric constant for the P700CA 0 protein region be OV3.…”

Section: Pro¢le Of Changes Of the E¡ective Dielectric Constant Along mentioning

confidence: 99%

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Photoelectric studies of the transmembrane charge transfer reactions in photosystem I pigment‐protein complexes

2003

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The results of studies of charge transfer in cyanobacterial photosystem I (PS I) using the photoelectric method are reviewed. The electrogenicity in the PS I complex and its interaction with natural donors (plastocyanin, cytochrome c 6 ), natural acceptors (ferredoxin, £avodoxin), or arti¢cial acceptors and donors (methyl viologen and other redox dyes) were studied. The operating dielectric constant values in the vicinity of the charge transfer carriers in situ were calculated. The pro¢le of distribution of the dielectric constant along the PS I pigmentp rotein complex (from plastocyanin or cytochrome c 6 through the chlorophyll dimer P700 to the acceptor complex) was estimated, and possible mechanisms of correlation between the local dielectric constant and electron transfer rate constant were discussed. ß

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Section: Electrogenic Reactions At the Acceptor Side Of Ps Isupporting

confidence: 83%

Section: Introductionmentioning

confidence: 87%

Section: Profile Of Changes Of the Effective Dielectric Constant Alonmentioning

confidence: 99%

Section: Pro¢le Of Changes Of the E¡ective Dielectric Constant Along mentioning

confidence: 99%

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Photoelectric studies of the transmembrane charge transfer reactions in photosystem I pigment‐protein complexes

2003

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“…posomes-Excitation of oriented PS I complexes with a single turnover flash leads to the generation of a transmembrane electric potential difference from which the forward electron transfer rates and dielectrically weighted transmembrane distances can be measured (7,11,17). PS I complexes were incorporated into proteoliposomes, and the flash-induced response corresponded to the negative charging of the proteoliposome interior.…”

Section: Photovoltage Measurements On Ps I Complexes In Proteoli-mentioning

confidence: 99%

Recruitment of a Foreign Quinone into the A1 Site of Photosystem I

Semenov¹,

Vassiliev²,

Est³

et al. 2000

Journal of Biological Chemistry

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Interruption of the menA or menB gene in Synechocystis sp. PCC 6803 results in the incorporation of a foreign quinone, termed Q, into the A 1 site of photosystem I with a number of experimental indicators identifying Q as plastoquinone-9. A global multiexponential analysis of time-resolved optical spectra in the blue region shows the following three kinetic components: 1) a 3-ms lifetime in the absence of methyl viologen that represents charge recombination between P700؉ and an FeS ؊ cluster; 2) a 750-s lifetime that represents electron donation from an FeS ؊ cluster to methyl viologen; and 3) an ϳ15-s lifetime that represents an electrochromic shift of a carotenoid pigment. Room temperature direct detection transient EPR studies of forward electron transfer show a spectrum of P700 ؉ Q ؊ during the lifetime of the spin polarization and give no evidence of a significant population of P700 ؉ FeS ؊ for t < 2-3 s. The UV difference spectrum measured 5 s after a flash shows a maximum at 315 nm, a crossover at 280 nm, and a minimum at 255 nm as well as a shoulder at 290 -295 nm, all of which are characteristic of the plastoquinone-9 anion radical. Kinetic measurements that monitor Q at 315 nm show a major phase of forward electron transfer to the FeS clusters with a lifetime of ϳ15 s, which matches the electrochromic shift at 485 nm of the carotenoid, as well as an minor phase with a lifetime of ϳ250 s. Electrometric measurements show similar biphasic kinetics. The slower kinetic phase can be detected using timeresolved EPR spectroscopy and has a spectrum characteristic of a semiquinone anion radical. We estimate the redox potential of plastoquinone-9 in the A 1 site to be more oxidizing than phylloquinone so that electron transfer from Q ؊ to F X is thermodynamically unfavorable in the menA and menB mutants.The overall goal of these studies is to replace phylloquinone (vitamin K 1 ; 2-methyl-3-phytyl-1,4-naphthoquinone) in the A 1 site of photosystem I with a foreign quinone of different redox and/or kinetic properties but still capable of forward electron transfer to the FeS 1 clusters. In two previous papers, we described the construction and physiology of phylloquinone biosynthetic mutants in Synechocystis sp. PCC 6803 (1), and we reported EPR and electron nuclear double resonance studies that implied the presence of a foreign quinone, termed Q, in the A 1 site of PS I (2). To summarize briefly, the interruption of the menA and menB genes, which code for dihydroxynaphthoic acid synthase and phytyltransferase, respectively, results in the termination of phylloquinone biosynthesis as judged by high pressure liquid chromatography/mass spectroscopy (HPLC/ MS) and gas chromatography/mass spectroscopy of pigment extracts from isolated PS I complexes. However, the menA and menB mutant strains grow photoautotrophically under low light intensities, and isolated PS I complexes are capable of sustaining high rates of steady-state electron transfer from cytochrome c 6 to flavodoxin. HPLC and HPLC/MS studies show that quantita...

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Electrogenic Reactions Associated with Electron Transfer in Photosystem I

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Electrometrical study of electron transfer from the terminal F_A/F_B iron–sulfur clusters to external acceptors in photosystem I

Cited by 12 publications

References 21 publications

Photoelectric studies of the transmembrane charge transfer reactions in photosystem I pigment‐protein complexes

Photoelectric studies of the transmembrane charge transfer reactions in photosystem I pigment‐protein complexes

Recruitment of a Foreign Quinone into the A1 Site of Photosystem I

Electrogenic Reactions Associated with Electron Transfer in Photosystem I

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Electrometrical study of electron transfer from the terminal FA/FB iron–sulfur clusters to external acceptors in photosystem I

Cited by 12 publications

References 21 publications

Photoelectric studies of the transmembrane charge transfer reactions in photosystem I pigment‐protein complexes

Photoelectric studies of the transmembrane charge transfer reactions in photosystem I pigment‐protein complexes

Recruitment of a Foreign Quinone into the A1 Site of Photosystem I

Electrogenic Reactions Associated with Electron Transfer in Photosystem I

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Electrometrical study of electron transfer from the terminal F_A/F_B iron–sulfur clusters to external acceptors in photosystem I