Journal Article

Cyt <i>b</i>-559 (Fd) Participating in Cyclic Electron Transport in Spinach Chloroplasts: Evidence for Kinetic Connection with the Cyt <i>b</i><sub>6</sub>/f Complex

Sebastian Heimann and Ulrich Schreiber

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 8, pages 818-824
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029610
Cyt b-559 (Fd) Participating in Cyclic Electron Transport in Spinach Chloroplasts: Evidence for Kinetic Connection with the Cyt b6/f Complex

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A small fraction of low potential Cyt b-559, amounting to only 13% of total Cyt b-559 in spinach chloroplasts, is analyzed with the help of a highly selective, computer-controlled spectrophotometer, which simultaneously applies 16 pulse modulated narrow band measuring beams with wavelengths in the cytochrome α-band (500–600 nm) for recordings of time resolved difference spectra. This Cyt b-559 fraction remains oxidized upon dark incubation with ascorbate and is reduced upon illumination. It can be reduced by cyclic PSI in an antimycin A-sensitive reaction or in the course of antimycin A-insensitive linear electron transport via the Cyt b6/f complex. Reduction by NADPH in the dark requires ferredoxin. Simultaneous recordings of Cyt b-563 and Cyt f reveal close kinetic connection between this Cyt b-559 fraction and the low potential chain of the Cyt b6/f complex. These results confirm and extend previous observations of Miyake et al. 1995 (Plant Cell Physiol. 36: 743) in maize mesophyll thylakoids, which led to the hypothesis that Cyt b-559 (Fd) occupies the position of the postulated ferredoxin-plastoquinone reductase (FQR) in cyclic electron transport.

Keywords: Cyclic electron transport; Cyt b-559; Cyt b6/f complex; Q-cycle

Journal Article.  0 words. 

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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