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. 1988 Mar;7(3):589–594. doi: 10.1002/j.1460-2075.1988.tb02851.x

The photosynthetic water oxidase: its proton pumping activity is short-circuited within the protein by DCCD

Peter Jahns 1, Andrea Polle 1, Wolfgang Junge 1
PMCID: PMC454361  PMID: 16453830

Abstract

The photosynthetic water oxidase is composed of ˜15 polypeptides which are grouped around two functional parts: photosystem II and the catalytic manganese centre. Photochemically driven vectorial electron transfer between the manganese centre and bound plastoquinone causes deprotonation–protonation reactions at opposite sides of the thylakoid membrane. Thereby the water oxidase acts as a proton pump. Incubation of stacked thylakoids with N,N'-dicyclohexylcarbodiimide (DCCD) short-circuited its proton pumping activity. Under flashing light, the extent of both proton release into the lumen by water oxidation and of proton uptake from the medium by reduced quinone was diminished. Instead there was a rapid electrogenic backreaction with a strong H/D-isotope effect. Apparently protons which were produced by water oxidation were channelled across the transmembrane protein to the bound quinone. A more rapid protonation of the reduced quinone was evident from a shortening of the time lag for the reduction of photosystem I. These effects were paralleled by the preferential labelling with [14C]DCCD in stacked thylakoids of two polypeptides with 20 and 24 kd apparent molecular mass. These may be capping the oxidizing and the reducing terminus of the water oxidase to control proton extrusion and proton uptake respectively.

Keywords: photosynthesis, photosystem II, proton pump, water oxidase, DCCD

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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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