INVOLVEMENT OF PLASTOQUINONE BOUND WITHIN THE ISOLATED CYTOCHROME-B6-F COMPLEX FROM CHLOROPLASTS IN OXIDANT-INDUCED REDUCTION OF CYTOCHROME-B6

作     者：HURT, E HAUSKA, G 

作者机构：UNIV REGENSBURG INST BOT D-8400 REGENSBURG FED REP GER 

出 版 物：《BIOCHIMICA ET BIOPHYSICA ACTA》 (生物化学与生物物理学报 - 生物能学)

年 卷 期：1982年第682卷第3期

页      面：466-473页

核心收录：

学科分类：0710[理学-生物学] 071010[理学-生物化学与分子生物学] 07[理学] 

基　　金：Deutsche Forschungsgemeinschaft  DFG  (SFB 43/C2) 

主　　题：Electron transport Cytochrome b6-f complex Plastoquinone Cytochrome b6 (Chloroplast) 

摘      要：Oxidant-induced reduction of cytochrome [Cyt] b6 is completely dependent on a reduced component within the isolated Cyt B6-f complex. This component can be reduced by dithionite or by NADH/N-methylphenazonium methosulfate. It is a 2H+/2e- carrier with a midpoint potential of 100 mV at pH 7.0, which is very similar to the midpoint potential of the plastoquinone pool in chloroplasts. Oxidant-induced reduction of Cyt b6 is stimulated by plastoquinol-1 as well as by plastoquinol -90. The midpoint potential of the transient reduction of Cyt b/6 was not shifted by added plastoquinol. Quinone analysis of the purified Cyt b6-f complex revealed .apprx. 1 plastoquinone/Cyt f. The endogenous quinone is heterogeneous, a form more polar than plastoquinone A, probably plastoquinone-C, dominating. This is different from the thylakoid membrane where plastoquinone-A is the main quinone. The endogenous quinone can be extracted from the lyophilized Cyt b6-f complex by acetone, but not by hydrocarbon solvents. Oxidant-induced reduction of Cyt b6 was observed in the lyophilized and hexane-extracted complex, but was lost in the acetone-extracted complex. Reconstitution was achieved either with plastoquinol-1 or plastoquinol-9, suggesting that a plastoquinol molecule is involved in oxidant-induced reduction of Cyto b6.