Article ID Journal Published Year Pages File Type
29891 Journal of Photochemistry and Photobiology B: Biology 2016 9 Pages PDF
Abstract

•Treatment of PSII by F−, NH4Cl, acetate results in appearance of split EPR signal and decoupling effect.•We imply that these inhibitors disturb the hydrogen bond network around Ca2 +.•All investigated inhibitors have other inhibition sites at higher concentrations.

Ca2 + extraction from oxygen-evolving complex (OEC) of photosystem II (PSII) is accompanied by decoupling of oxygen evolution/electron transfer processes [Semin et al. Photosynth. Res. 98 (2008) 235] and appearance of a broad EPR signal at g = 2 (split “S3” signal) what can imply the relationship between these effects. Split signal have been observed not only in Ca-depleted PSII but also in PSII membranes treated by fluoride anions, sodium acetate, and NH4Cl. Here we investigated the question: can such compounds induce the decoupling effect during treatment of PSII like Ca2 + extraction does? We found that F−, sodium acetate, and NH4Cl inhibit O2 evolution in PSII membranes more effectively than the reduction of artificial electron acceptor 2,6-dichlorophenolindophenol, i.e. the action of these compounds is accompanied by decoupling of these processes in OEC. Similarity of effects observed after Ca2 + extraction and F−, CH3COO− or NH4Cl treatments suggests that these compounds can inactivate function of Ca2 +. Such inactivation could originate from disturbance of the network of functionally active hydrogen bonds around OEC formed with participation of Ca2 +. This inhibition effect is observed in the region of low concentration of inhibitors. Increasing of inhibitor concentration is accompanied by appearance of other sites of inhibition.

Related Topics
Physical Sciences and Engineering Chemical Engineering Bioengineering
Authors
, ,