Kunert K J, Böhme H, Böger P
Biochim Biophys Acta. 1976 Dec 6;449(3):541-53. doi: 10.1016/0005-2728(76)90163-8.
Chloroplast material active in photosynthetic electron transport has been isolated from Scenedesmus acutus (strain 270/3a). During homogenization, part of cytochrome 553 was solubilized, and part of it remained firmly bound to the membrane. A direct correlation between membrane cytochrome 553 and electron transport rates could not be found. Sonification removes plastocyanin, but leaves bound cytochrome 553 in the membrane. Photooxidation of the latter is dependent on added plastocyanin. In contrast to higher plant chloroplasts, added soluble cytochrome 553 was photooxidized by 707 nm light without plastocyanin present. Reduced plastocyanin or cytochrome 553 stimulated electron transport by Photosystem I when supplied together or separately. These reactions and cytochrome 553 photooxidation were not sensitive to preincubation of chloroplasts with KCN, indicating that both redox proteins can donate their electrons directly to the Photosystem I reaction center. Scenedesmus cytochrome 553 was about as active as plastocyanin from the same alga, whereas the corresponding protein from the alga Bumilleriopsis was without effect on electron transport rates. It is suggested that besides the reaction sequence cytochrome 553 leads to plastocyanin leads to Photosystem I reaction center, a second pathway cytochrome 553 leads to Photosystem I reaction center may operate additionally.
已从尖锐栅藻（菌株270/3a）中分离出在光合电子传递中具有活性的叶绿体物质。在匀浆过程中，部分细胞色素553被溶解，部分仍与膜紧密结合。未发现膜结合的细胞色素553与电子传递速率之间存在直接相关性。超声处理可去除质体蓝素，但膜中仍保留结合态的细胞色素553。后者的光氧化作用依赖于添加的质体蓝素。与高等植物叶绿体不同，在没有质体蓝素的情况下，添加的可溶性细胞色素553可被707 nm光光氧化。当一起或分别提供时，还原型质体蓝素或细胞色素553可刺激光系统I的电子传递。这些反应以及细胞色素553的光氧化作用对叶绿体用KCN预孵育不敏感，这表明这两种氧化还原蛋白均可将其电子直接提供给光系统I反应中心。尖锐栅藻的细胞色素553的活性与来自同一藻类的质体蓝素相当，而来自藻类布氏藻属的相应蛋白对电子传递速率没有影响。有人提出，除了细胞色素553→质体蓝素→光系统I反应中心的反应序列外，可能还存在另一条细胞色素553→光系统I反应中心的途径。
