摘要
寡霉索可抑制光下DTT激活的Mg^(2+)-ATP酶活力并促进质子流出,这两种效应对温度的反应相似,并受膜能化状态的影响。 寡霉素对在光下以胰蛋白酶激活的叶绿体膜上Mg^(2+)-ATPase和脱离了膜的Ca^(2+)-ATPase都有抑制作用,但对经NEM修饰的叶绿体膜上Mg^(2+)-ATPase活力没有影响,且其促进质子流出的效应也消失,在暗中经胰蛋白酶活化的Ca^(2+)-ATPase对寡霉素不敏感。由此推断寡霉素抑制光激活的ATPase和促进质子流出的效应是光引起膜能化导致CF_1变构,γ亚基暴露,而使寡霉素能与之结合的结果,因此寡霉素在叶绿体上的作用部位是在CF_1中,而与线粒体在F_0上有所不同。
The inhibitory effect of oligomycin on the activity of membrane Mg^(2+)ATPase activated by light with DTT was influenced by temperature. Such effect reached its maximum at 20℃ (Fig. 1). The promotive effect of oligomycin on the rate of H_(in)^+ efflux was also influenced by temperature which has an inhibitory effect on the activity of membrane ATPase (Fig. 2).
These two effects were observed when NH_4Cl concentration was at 1×10^(-5) mol/L or 1×10^(-4) mol/L, which had no influence on the rise of pH of chloroplast suspension caused by light, and they disappeared when NH_4Cl concentration was at 1×10^(-3) mol/L, and pH increased by about 50% over that with no added NH_4Cl (Fig. 3, 4).
The soluble Ca^(2+)-ATPase activated by trypsin in the dark was not influenced by oligomycin (Table 2). The treatment of chloroplast by TPCKtrypsin in light resulted in highly active Mg^(2+)-ATPase from CF_1 on membrahe and Ca^(2+)-ATPase of soluble CF_1. Illumination induced some conformational changes of the enzyme, which caused the exposure of γ-subunit and easy digestion by trypsin. Both ATPases with exposed γ-subunit were highly sensitive to oligomycin. the action site of which was shown to be on the γ-subunit of CF_1 (Table 1).
The Mg^(2+)-ATPase activated by TPCK-trypsin of chloroplast treated with NEM, a γ-subunit modifying agent, was (?)ot affected by oligomycin, and the promotive effect of oligomycin on the H_(in)^+ efflux disappeared (Table 3, Fig. 5).
The results indicated that the action of oligomycin on γ-subunit induced the conformational changes of CF_1, thus, affecting the functions of ATPase.
基金
国家自然科学基金
关键词
叶绿体
寡霉素
oligomycin
NEM
dithiothreitol
oligomycin sensitivity conferring protein
CF_(8)
CF_（2）
