Antimycin A inhibits cytochrome b 559-mediated cyclic electron flow within photosystem II

Antimycin A inhibits cytochrome b 559-mediated cyclic electron flow within photosystem II The light reactions of photosynthesis are known to comprise both linear and cyclic electron flow in order to convert light energy into chemical energy in the form of NADPH and ATP. Antimycin A (AA) has been proposed as an inhibitor of ferredoxin-dependent cyclic electron flow around photosystem I (CEF-PSI) in photosynthesis research. However, its precise inhibitory mechanism and target site had not been elucidated yet. Here we show that AA inhibits the cyclic (alternative) elec- tron flow via cytochrome b (Cyt b ) within photosystem II (CEF-PSII). When AA was applied to thylakoid membranes 559 559 isolated from spinach leaves, the high potential form of Cyt b , which was reduced in the dark, was transformed into the lower potential forms and readily oxidized by molecular oxygen. In the absence of AA, the reduced Cyt b was oxidized by P680 upon light illumination and re-reduced in the dark, mainly by the electron from the Q site on the acceptor side of PSII. In contrast, AA suppressed the oxidation of Cyt b and induced its reduction under the illumination. This inhibition of Cyt b oxidation by AA enhanced photoinhibition of PSII. Based on the above results, we propose caution regarding http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Photosynthesis Research Springer Journals

Antimycin A inhibits cytochrome b 559-mediated cyclic electron flow within photosystem II

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Publisher
Springer Journals
Copyright
Copyright © 2018 by Springer Science+Business Media B.V., part of Springer Nature
Subject
Life Sciences; Plant Sciences; Plant Physiology; Biochemistry, general; Plant Genetics and Genomics
ISSN
0166-8595
eISSN
1573-5079
D.O.I.
10.1007/s11120-018-0519-7
Publisher site
See Article on Publisher Site

Abstract

The light reactions of photosynthesis are known to comprise both linear and cyclic electron flow in order to convert light energy into chemical energy in the form of NADPH and ATP. Antimycin A (AA) has been proposed as an inhibitor of ferredoxin-dependent cyclic electron flow around photosystem I (CEF-PSI) in photosynthesis research. However, its precise inhibitory mechanism and target site had not been elucidated yet. Here we show that AA inhibits the cyclic (alternative) elec- tron flow via cytochrome b (Cyt b ) within photosystem II (CEF-PSII). When AA was applied to thylakoid membranes 559 559 isolated from spinach leaves, the high potential form of Cyt b , which was reduced in the dark, was transformed into the lower potential forms and readily oxidized by molecular oxygen. In the absence of AA, the reduced Cyt b was oxidized by P680 upon light illumination and re-reduced in the dark, mainly by the electron from the Q site on the acceptor side of PSII. In contrast, AA suppressed the oxidation of Cyt b and induced its reduction under the illumination. This inhibition of Cyt b oxidation by AA enhanced photoinhibition of PSII. Based on the above results, we propose caution regarding

Journal

Photosynthesis ResearchSpringer Journals

Published: May 22, 2018

References

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