In Chromatium, a single photochemical reaction center oxidizes both cytochrome C552 and cytochrome C555

Parson, Walther; Case, George D.

doi:10.1016/0005-2728(70)90253-7

Cited by 137 publications

(40 citation statements)

References 26 publications

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“…This provides further support for the generality that photosynthetic bacteria are equipped with only one oytochrome-linked light reaction (see [9,28,29,30]). Fig.…”

Section: Components Of the Light Reactionmentioning

confidence: 53%

“…Arrangements in which two electron donors share a single acceptor is not without precedence in the literature of photosynthetic research [9,28--301; there are several species of photosynthetic bacteria in which two cytochromes are complexed with and in competition for a single oxidant. I n ChromatiumD for example [28,29], cytochrome cj53 (the subscript here represents the reduced absorbance maximum in the &-band region) with a midpoint potential of +I0 mV is photooxidized (tl,, 1 psec) by the reaction-center bacteriochlorophyll (midpoint potential +480 mV) in preference to cytochrome c, , , , midpoint potential +330 mV (hi, 2 psec). Cytochrome c553 has for sometime been considered to be on a substrate-linked noncyclic electron pathway while cytochrome c,,, is a member of the cyclic electron pathway.…”

Section: Components Of the Light Reactionmentioning

confidence: 99%

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Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Dutton

Jackson

1972

European Journal of Biochemistry

183

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1. The b-and c-type cytochromes in chromatophores from photosynthetically grown Rhodospirillum rubrum and Rhodopseudomonas spheroides have been characterized in situ in terms of their oxidation-reduction potential properties.I n R. rubrum only one cytochrome c measured a t 551-540 nm was resolved potentiometrically; the midpoint potential a t pH 7.2, Em7.2, is +293 mV. Three cytochrome species measured a t 562-540 nm were resolved; they had Em7.2 values + 170 mV, -5 mV and -105 mV and were tentatively identified with cytochrome b, cc' and b respectively; they contributed to the over-all absorbance change in the ratio 8 : 25 : 17, respectively. I n Rps. spheroides the Em7.0 of cytochrome c is + 295 mV. Three cytochromes tentatively considered to be of the b-type have Em7.2 values of + 155 mV, +50 mV and -90 mV; their approximate reduced minus oxidized maxima were determined to be 558-9 nm, 560 nm and 564 nm, respectively. The approximate relative absorbance ratio given at the reduced minus oxidized maxima was 8 : 21 : 14. 3. A working model for electron transfer in Rps. spheroides based on the measured thermodynamic and kinetic properties is presented.

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“…This provides further support for the generality that photosynthetic bacteria are equipped with only one oytochrome-linked light reaction (see [9,28,29,30]). Fig.…”

Section: Components Of the Light Reactionmentioning

confidence: 53%

Section: Components Of the Light Reactionmentioning

confidence: 99%

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Dutton

Jackson

1972

European Journal of Biochemistry

183

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“…The more loosely bound UQ is not required for the primary photochemistry and probably represents the secondary electron acceptor (6,26). The ease of displacement of this UQ by o-phenanthroline offers a simple explanation of the inhibitory effect of o-phenanthroline on electron transfer to secondary electron acceptors (27). A possible mechanism of the removal of the UQ's by o-phenanthroline is the latter's binding to Fe2+, thereby displacing the UQ's.…”

Section: Discussionmentioning

confidence: 99%

Primary acceptor in bacterial photosynthesis: obligatory role of ubiquinone in photoactive reaction centers of Rhodopseudomonas spheroides.

Okamura¹,

Isaacson²,

Fehér³

1975

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

412

230

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Reaction centers were found to bind two ubiquinones, both of which could be removed by o-phenanthroline and the detergent lauryldimethylamine oxide. One ubiquinone was more easily removed tan the other. The lowtemperature light-induced optical and electron paramagnetic resonance (EPR) changes were eliminated and restored upon removal and readdition of ubiquinone and were quantitatively correlated with the amount of tightly bound ubiquinone. We, therefore, conclude that this ubiquinone plays an obligatory role in the primary photochemistry. The easily removed ubiquinone is thought to be the secondary electron acceptor. The low-temperature charge recombination kinetics, as well as the optical and EPR spectra, were the same for untreated reaction centers and for those reconstituted with ubiquinone. This indicates that extraction and reconstitution were accomplished without altering the conformation of the active site. Reaction centers reconstituted with other quinones also showed restored photochemical activity, although they exhibited changes in their low-temperature recombination kinetics and light-induced ( The presence of stoichiometric amounts of iron in RC's (7) and the observation of a broad electron paramagnetic resonance (EPR) signal (7-9) led to the hypothesis that iron was the primary acceptor. This hypothesis was questioned by Loach and Hall, who reported full photochemical activity in iron-depleted preparations (10). They observed a new, narrow, light-induced EPR signal that was shown to be due to a ubiquinone (UQ) radical (11, 12

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“…from Qn7 is substantially slower than from QI: although the observed kinetics are variable [32]. Support for the reconstitution of the Q1 to Qn electron transfer reaction in the RC-phospholipidoctane solution is presented in fig.2C which shows the effect of o-phenanthroline, an inhibitor of the Q1 to Qn electron transfer reaction ( [31] and see [ 11). In the presence of o-phenanthroline the (BChl),?…”

Section: Lmentioning

confidence: 91%

Reconstitution de photochemically active reaction centers in planar phospholipid membranes

Packham

Müeller

et al. 1980

FEBS Letters

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In Chromatium, a single photochemical reaction center oxidizes both cytochrome C552 and cytochrome C555

Cited by 137 publications

References 26 publications

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Primary acceptor in bacterial photosynthesis: obligatory role of ubiquinone in photoactive reaction centers of Rhodopseudomonas spheroides.

Reconstitution de photochemically active reaction centers in planar phospholipid membranes

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