Spectrally distinct cytochrome b -563 components in a chloroplast cytochrome b — f complex: Interaction with a hydroxyquinoline N -oxide
- 1 October 1983
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 80 (20), 6249-6253
- https://doi.org/10.1073/pnas.80.20.6249
Abstract
The 2 heme equivalents of cytochrome b-563 in the photosynthetic cytochrome b-f complex [from spinach] can be distinguished by their rate of reduction with dithionite at 25.degree. C and by their optical absorption spectra at 77 K. The cytochrome b component that is rapidly reduced after addition of dithionite or reduced ferredoxin possesses an .alpha. band that splits at 77 K into 2 peaks, at 557 and 561 nm. Prolonged incubation with reductant reveals a 2nd, approximately equimolar cytochrome b component that has at 77 K an unsplit .alpha.-band maximum at 561 nm. The designations cytochrome b-563H and cytochrome b-563L, respectively, are proposed for the rapidly and more slowly reduced cytochrome b-563 components. Potentiometric titration establishes a midpoint potential, Em, of -30 mV (electron change n .simeq. 2) for cytochrome b-563H and -150 mV (n = 1) for cytochrome b-563L at pH 7.5. The reduction potential of these components is raised by 2-heptyl-4-hydroxyquinoline N-oxide, giving Em values of +57 and -34 mV, respectively, with each titration slope approximating n = 2.This publication has 22 references indexed in Scilit:
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