Binding Affinities of Oxidized and Reduced Forms of Tetrahalogenated Benzoquinones to the Q_B Site in Oxygen-Evolving Photosystem II Particles from Synechococcus elongatus : MEMBRANES AND BIOENERGETICS

概要

論文の詳細を見る
Binding affinities of the Q_B Site for four tetrahalogenated benzoquinones (THBQs) were investigated by measuring their ability to serve as electron acceptors or act as inhibitors of oxygen evolution in Synechococcus photosystem II particles. Iodanil, bromanil and chloranil but not fluoranil induced a rapid oxidation of Q_A^- and doubled the area over the fluorescence induction curve, indicating dark oxidation of Q_<400>. Analyses of these two THBQ-induced reactions and inhibition of the accelerated Q_A^- oxidation by DCMU yielded binding constants of the quinones comparable to those determined from measurements of oxygen evolution. Generally, THBQs bound tightly to the Q_B site. However, the binding affinity varied in a wide range with THBQs. The Q_B site bound iodanil with an extremely high affinity but fluoranil relatively weakly. The hydroquinone forms of the THBQs also bound to the Q_B site and inhibited Q_A^- oxidation by Q_B. The concentrations of the hydroquinones required for 50% inhibition of Q_A^- oxidation suggest that the Q_B site binds the hydroquinones more weakly than the corresponding quinones except for fluoranil, which binds to the Q_B site more tightly in its reduced form than in oxidized one. The abilities of THBQs to function as electron acceptors or inhibitors of oxygen evolution, and as oxidants of Q_<400> in the dark, are discussed in relation to the binding affinities of the quinones to the Q_B site.
日本植物生理学会の論文

Binding Affinities of Oxidized and Reduced Forms of Tetrahalogenated Benzoquinones to the Q_B Site in Oxygen-Evolving Photosystem II Particles from Synechococcus elongatus : MEMBRANES AND BIOENERGETICS

スポンサーリンク

概要

著者

関連論文

スポンサーリンク