Effects of 1,N^6-ethenoadenylates on the regulation of photosynthetic activities by adenylates; A study of the nucleotide binding sites on chloroplast coupling factor 1
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概要
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Effects of 1,N^6-ethenoadenylates (ε-adenylates) were tested on phosphorylation, and electron transport under phosphorylation, arsenylation and quasi-arsenylation (stimulation of electron transport in the presence of ATP, AMP and arsenate) conditions in isolated spinach chloroplasts ε-ATP as well as ATP partially inhibited ferricyanide reduction through binding to the chloroplast coupling factor I with an apparent dissociation constant (K_D^<app>) of around 50 μm, which was remarkably larger than that for ATP (ca. 2 μM). ε-ATP at below 500 μM had no effect on phosphorylation but inhibited quasi-arsenylation in competition with ATP with an apparent inhibition constant (K_i^<app>) of around 60 μM. ε-ADP as well as ADP partially inhibited ferricyanide reduction with a K_D^<app> value close to that for ε-ATP. ε-ADP was phosphorylated (the apparent Michaelis constant, K_m^<app>=80 μM) accompanying stimulation of ferricyanide reduction to the magnitude predicted (P/Δe= 1). ε-ADP-arsenylation was also detected by stimulation of ferricyanide reduction. ε-AMP alone caused little inhibition of ferricyanide reduction as AMP, but competitively depressed the electron transport inhibition by ADP and ATP with a K_i^<app> value of around 200 μM. ε-AMP was not effective for ADP phosphorylation but inhibited stimulation due to quasiarsenylation coupling in competition with AMP (K_i^<app> = 150 μM) Among the possible combinations ofadenylates and ε-adenylates for quasiarsenylation, only [ATP+AMP] could couple with the energy transduction mechanism. Based on the specificity of binding sites to adenylates and ε-adenylates, an attempt was made to distinguish at least four (two pairs) kinds of binding sites (at least six sites in toto) on the chloroplast coupling factor 1 for photosynthetic energy transduction. When one pair of sites is occupied by the designated adenylates or ε-adenylates (allosteric effectors), the coupling factor is thought to be in a conformation for coupling with the energy transduction mechanism in the presence of phosphate or arsenate.
- 日本植物生理学会の論文
- 1976-08-00
著者
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Sugiyama Yasuo
Department Of Biology Faculty Of Science
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Sugiyama Yasuo
Department Of Biology Faculty Of Science Osaka University
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Mukohata Yasuo
Department Of Biology Faculty Of Science
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