Rates of vectorial proton transport supported by cyclic electron flow during oxygen reduction by illuminated intact chloroplasts
Rates of vectorial proton transport supported by cyclic electron flow during oxygen reduction by illuminated intact chloroplasts
复制标题
照明完整叶绿体氧还原过程中循环电子流支持的矢量质子传输速率
DOI：
10.1007/bf02183044
复制
发表时间：
1994
影响因子：
3.7
通讯作者：
U. Heber
中科院分区：
文献类型：
--
作者：
Y. Kobayashi;U. Heber
9-氨基吖啶荧光的光依赖猝灭被用来监测在存在或不存在外部电子受体的情况下，受照完整叶绿体中跨类囊体质子梯度的状态。在厌氧条件下，没有可察觉的依赖于光的荧光猝灭，表明在没有外部电子受体的情况下，耦合电子传递受到抑制。氧气解除了这种抑制。然而，当DCMU在无氧条件下抑制了质苷库的过度还原时，即使在厌氧条件下，耦合的循环电子传递也支持跨类囊体质子梯度的形成。这种质子梯度在氧气的存在下坍塌了。在好氧条件下，当KCN抑制核酮糖二磷酸羧基酶和抗坏血酸过氧化物酶时，荧光猝灭表明形成了跨类囊体质子梯度，在以相似的线性电子传递速率进行的Mehler反应中，氧气的作用大于甲基紫精。显然，当氧作为电子受体时，循环电子传递与线性电子传递同时发生，而当甲基紫精接受来自光系统I的电子时，循环电子传递与线性电子传递不同时发生。低浓度的DCMU可以提高循环电子传递与线性电子传递的比率。这表明，即使在有氧条件下，孤立的完整叶绿体中的循环电子传递也受到电子载体过度还原的限制。事实上，在光照条件下，光系统I反应中心的P700在叶绿体中仍然被还原，这导致了叶片中P700的广泛氧化。这表明，光系统II活性的调节在分离的叶绿体中不如在叶片中有效。假设在慢线性电子传输过程中，Q循环支持H+/e为3，则可以计算耦合到依赖于光系统I的循环电子流的矢量质子输运。在完整叶绿体中，光系统I依赖的质子转运的最高速率为330mgmolProton(mgμh)−1。当H+/e不是3而是2时，质子转移不是330而是220moLμ(Mg Chl H)−1。讨论了叶绿体和叶片中循环电子传递调控的差异。
The light-dependent quenching of 9-aminoacridine fluorescence was used to monitor the state of the transthylakoid proton gradient in illuminated intact chloroplasts in the presence or absence of external electron acceptors. The absence of appreciable light-dependent fluorescence quenching under anaerobic conditions indicated inhibition of coupled electron transport in the absence of external electron acceptors. Oxygen relieved this inhibition. However, when DCMU inhibited excessive reduction of the plastoquinone pool in the absence of oxygen, coupled cyclic electron transport supported the formation of a transthylakoid proton gradient even under anaerobiosis. This proton gradient collapsed in the presence of oxygen. Under aerobic conditions, and when KCN inhibited ribulose bisphosphate carboxylase and ascorbate peroxidase, fluorescence quenching indicated the formation of a transthylakoid proton gradient which was larger with oxygen in the Mehler reaction as electron acceptor than with methylviologen at similar rates of linear electron transport. Apparently, cyclic electron transport occured simultaneously with linear electron transport, when oxygen was available as electron acceptor, but not when methylviologen accepted electrons from Photosystem I. The ratio of cyclic to linear electron transport could be increased by low concentrations of DCMU. This shows that even under aerobic conditions cyclic electron transport is limited in isolated intact chloroplasts by excessive reduction of electron carriers. In fact, P700in the reaction center of Photosystem I remained reduced in illuminated isolated chloroplasts under conditions which resulted in extensive oxidation of P700in leaves. This shows that regulation of Photosystem II activity is less effective in isolated chloroplasts than in leaves. Assuming that a Q-cycle supports a H+/e ratio of 3 during slow linear electron transport, vectorial proton transport coupled to Photosystem I-dependent cyclic electron flow could be calculated. The highest calculated rate of Photosystem I-dependent proton transport, which was not yet light-saturated, was 330 μmol protons (mg chlorophyll h)−1in intact chloroplasts. If H+/e is not three but two proton transfer is not 330 but 220 μmol (mg Chl H)−1. Differences in the regulation of cyclic electron transport in isolated chloroplasts and in leaves are discussed.
登录
查看更多内容
Henning Hormann：“在没有甲基 vidogen 的情况下，完整叶绿体显示 O^2 还原的最佳 pH5：超氧化物质子化调节作用的证据”
DOI：
--
发表时间：
--
期刊：
影响因子：
--
作者：
通讯作者：
--
Henning Hormann：“在没有甲基紫精的情况下，完整叶绿体显示 O_2 还原的最佳 pH 为 5：超氧化物质子化调节作用的证据。”
DOI：
--
发表时间：
--
期刊：
影响因子：
--
作者：
通讯作者：
--
影响因子：
4.9
作者：
K. Asada;U. Heber;U. Schreiber
通讯作者：
K. Asada;U. Heber;U. Schreiber
Ejiri，S.；Kawamura，R.；
DOI：
--
发表时间：
--
期刊：
影响因子：
--
作者：
通讯作者：
--
K.Asada：“通过监测 P700 和叶绿素荧光的氧化还原变化，在完整叶子中检测到从基质成分到系统间链的电子流和玉米叶绿体中的循环电子流”
DOI：
--
发表时间：
--
期刊：
影响因子：
--
作者：
通讯作者：
--