Electron transfer proteins of chloroplast envelope

我们发现，减少外叶绿体细胞色素（Cyt）c照明完整的叶绿体。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。通过使用还原的Cyt c的氧化，氧化还原物质被鉴定为蛋白质与具有类似于质体醌的E^的物质的多聚体复合<o1>物。DCMU能抑制完整叶绿体对Cyt c的还原，而DBMIB对Cyt c的还原无抑制作用，说明叶绿体电子传递过程中，叶绿体外膜接受质体醌位点的电子。加入Cyt c后，CO2固定率和CO2依赖性放氧率均降低。类囊体膜的环状和非环状磷酸化被单独的包膜抑制。这些光合活性的下降并不是由于电子通过被膜电子转移耗散到Cyt c的结果，因为Cyt c的减少量远小于放氧产量的下降，被膜电子转移可能是一种独特的反应，它使类囊体和/或叶绿体之间的光合产量相等。

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.