Cytochrome photooxidation at liqud nitrogen temperatures in photosynthetic bacteria

Kihara, Toru; Chance, Britton

doi:10.1016/0005-2728(69)90232-1

Cited by 57 publications

(14 citation statements)

References 7 publications

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“…The recombination effectively removes the oxidant for the CP + QA ~ C + PQA reaction. This would not significantly affect the extent of oxidation of the low potential Cyt c553, since its oxidation rate at 77 K has been reported to be much faster than the competing recombination reaction [17]. This simple explanation may not be adequate to account for the "freezing-out" of high potential cytochrome activity in all species, such as Rps.…”

Section: Discussionmentioning

confidence: 90%

“…However, the fact that, at low temperature, the oxidation of the high potential heroes freezes out at moderate redox potentials, whereas oxidation of the low potential heme, at low potentials, does not, clearly implies that, in the context of this model, the interheme transfer does not fail and continues to be rapid [17]. In fact, it is necessary to suppose that the influence of the redox state of Cyt c553 on the kinetic properties of the high potential heme is such that reduction of the low potential heme facilitates electron donation from Cyt c559 to P+ both at room temperature, as described above, and at low temperature.…”

Section: Discussionmentioning

confidence: 99%

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Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis

et al. 1987

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The initial oxidized species in the photochemical charge separation in reaction centers from Rps. viridis is the primary donor, P(+), a bacteriochlorophyll dimer. Bound c-type cytochromes, two high potential (Cyt c 558) and two low potential (Cyt c 553), act as secondary electron donors to P(+). Flash induced absorption changes were measured at moderate redox potential, when the high potential cytochromes were chemically reduced. A fast absorption change was due to the initial oxidation of one of the Cyt c 558 by P(+) with a rate of 3.7×10(6)s(-1) (τ=270nsec). A slower absorption change was attributable to a transfer, or sharing, of the remaining electron from one high potential heme to the other, with a rate of 2.8×10(5)s(-1) (τ=3.5 μsec). The slow change was measured at a number of wavelengths throughout the visible and near infrared and revealed that the two high potential cytochromes have slightly different differential absorption spectra, with α-band maxima at 559 nm (Cyt c 559) and 556.5 nm (Cyt c 556), and dissimilar electrochromic effects on nearby pigments. The sequence of electron transfers, following a flash, is: Cyt c 556→Cyt c 559→P(+). At lower redox potentials, a low midpoint potential cytochrome, Cyt c 553, is preferentially oxidized by P(+) with a rate of 7×10(6)s(-1) (τ=140 nsec). The assignment of the low and high potential cytochromes to the four, linearly arranged hemes of the reaction center is discussed. It is concluded that the closest heme to P must be the high potential Cyt c 559, and it is suggested that a likely arrangement for the four hemes is: c 553 c 556 c 553 c 559P.

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Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis

et al. 1987

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“…Kihara and Chance have undertaken an immense study of the low-temperature cytochrome oxidation of different species of photosynthesizing bacteria (Kihara and Chance 1969).…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of cytochrome photooxidation and conformational dynamics of Chromatium reaction center complexes

et al. 1989

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A temperature dependence of multiheme cytochrome c oxidation induced by a laser pulse was studied in photosynthetic reaction center preparations from Chromatium minutissimum. Absorbance changes and kinetic characteristics of the reaction were measured under redox conditions where one or all of the hemes of the cytochrome subunit are chemically reduced (E h =+300 mV or E h =-20 to -60 mV respectively). In the first case photooxidation is inhibited at temperatures lower than 190-200 K with the rate constant of the photooxidation reaction being practically independent on temperature over the range of 300 to 190 K (k=2.2×10(5) s(-1)). Under reductive conditions (E h =-20 to -60 mV) lowering the temperature to 190-200 K causes the reaction to slow from k=8.3×10(5) s(-1) to 2.1×10(4) s(-1). Under further cooling down to the liquid nitrogen temperature, the reaction rate changes negligibly. The absorption amplitude decreases by 30-40% on lowering the temperature. A new physical mechanism of the observed critical effects of temperature on the rate and absorption amplitude of the multiheme cytochrome c oxidation reaction is proposed. The mechanism suggests a close interrelation between conformational mobility of the protein and elementary electron tunneling act. The effect of "freezing" conformational motion is described in terms of a local diffusion along a random rough potential.

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“…Toru Kihara examined many species of bacteria and characterized the low temperature photooxidation of both high and low-potential cytochromes in them (Kihara and Chance 1969).…”

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confidence: 99%

Tunneling enters biology

DeVault

1989

Photosynth Res

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Cytochrome photooxidation at liqud nitrogen temperatures in photosynthetic bacteria

Cited by 57 publications

References 7 publications

Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis

Kinetics of oxidation of the bound cytochromes in reaction centers from Rhodopseudomonas viridis

Temperature dependence of cytochrome photooxidation and conformational dynamics of Chromatium reaction center complexes

Tunneling enters biology

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