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. 1977 Oct;60(4):592–596. doi: 10.1104/pp.60.4.592

Photophosphorylation Associated with Photosystem II

II. Effects of Electron Donors, Catalyst Oxidation, and Electron Transport Inhibitors on Photosystem II Cyclic Photophosphorylation

Charles F Yocum 1
PMCID: PMC542670  PMID: 16660144

Abstract

Incubation of KCN-Hg-NH2OH-inhibited spinach (Spinacia oleracea L.) chloroplasts with p-phenylenediamine for 10 minutes in the dark prior to illumination produced rates of photosystem II cyclic photophosphorylation up to 2-fold greater than the rates obtained without incubation. Partial oxidation of p-phenylenediaine with ferricyanide produced a similar stimulation of ATP synthesis; addition of dithiothreitol suppressed the stimulation observed with incubation. Addition of ferricyanide in amounts sufficient to oxidize completely p-phenylenediamine failed to inhibit completely photosystem II cyclic activity. This is due at least in part to the fact that the ferrocyanide produced by oxidation of p-phenylenediamine is itself a catalyst of photosystem II cyclic photophosphorylation. N,N,N′N′-Tetramethyl-p-phenylenediamine catalyzes photosystem II cyclic photophosphorylation at rates approaching those observed with p-phenylenediamine. The activities of both proton/electron and electron donor catalysts of the photosystem II cycle are inhibited by dibromothyoquinone and antimycin A. These findings are interpreted to indicate that photosystem II cyclic photophosphorylation requires the operation of endogenous membrane-bound electron carriers for optimal coupling of ATP synthesis to electron transport.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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