Electron transfer proteins of chloroplast envelope

我们发现在完整的叶绿体照射下，胞外色素（Cyt） c减少。该反应是由跨膜电子转移介导的，而不是由基质中产生的可溶性还原剂如超氧化物、过氧化氢或NAD(P)H介导的。通过对还原的Cyt c的氧化，re-dox物质被鉴定为与E^< 1>的物质(s)相似的蛋白质多聚物，与质体醌相似。氧化还原物质既存在于外膜，也存在于内膜。DCMU抑制了完整叶绿体对Cyt - c的还原，而DBMIB则没有，这表明在光合电子转移中，包膜电子转移接受来自质体醌位点的电子。Cyt c的加入降低了二氧化碳的固定速率和二氧化碳依赖的析氧速率。类囊体膜的环和非环光磷酸化被分离的包膜抑制。这些光合活性的下降不是电子通过包膜电子转移向Cyt c耗散的结果，因为Cyt c的减少量远小于析氧产率的下降。包膜电子转移可能是使类囊体和/或叶绿体之间的光合产量相等的独特反应。

We found the reduction of extrachloroplastic cytochrome (Cyt) c by illuminated intact chloroplasts. This reaction was mediated by a trans-envelope electron transfer but not by soluble reductants generated in stroma such as superoxide, hydrogen peroxide or NAD(P)H.By the use of the oxidation of the reduced Cyt c, re-dox substance was identified as a multimeric complex of proteins with substance (s) with E^<o1> which is similar to that of plastoquinone. The redox substances are localized both in outer and inner envelopes.Cyt c reduction by intact chloroplast was inhibited by DCMU but not by DBMIB which indicates that the envelope electron transfer accepts electrons from the plastoquinone site in the photosynthetic electron transfer. The rates of carbon dioxide fixation and carbon dioxide-dependent oxygen evolution were lowered by the addition of Cyt c. Cyclic and noncyclic photophosphorylations by thylakoid membranes were suppressed by the addition of isolated envelope membranes. These declines in photosynthetic activities were not the result of dissipation of electrons to Cyt c through envelope electron transfer because the reduced amount of Cyt c was much lesser than the decreased yield of oxygen evolution.Envelope electron transfer might be a unique reaction which equalizes the photosynthetic yield between thylakoids and/or chloroplasts.