Botanisches Institut der Universität München, Menzinger Strasse 67, D-8000, München 19, FRG.
Planta. 1988 Dec;176(4):488-96. doi: 10.1007/BF00397655.
A guanosine 5'-triphosphate (GTP)-dependent protein kinase was detected in preparations of outer chloroplast envelope membranes of pea (Pisum sativum L.) chloroplasts. The protein-kinase activity was capable of phosphorylating several envelope-membrane proteins. The major phosphorylated products were 23- and 32.5-kilo-dalton proteins of the outer envelope membrane. Several other envelope proteins were labeled to a lesser extent. Following acid hydrolysis of the labeled proteins, most of the label was detected as phosphoserine with only minor amounts detected as phosphothreonine. Several criteria were used to distinguish the GTP-dependent protein kinase from an ATP-dependent kinase also present in the outer envelope membrane. The ATP-dependent kinase phosphorylated a very different set of envelope-membrane proteins. Heparin inhibited the GTP-dependent kinase but had little effect upon the ATP-dependent enzyme. The GTP-dependent enzyme accepted phosvitin as an external protein substrate whereas the ATP-dependent enzyme did not. The outer membrane of the chloroplast envelope also contained a phosphotransferase capable of transferring labeled phosphate from [γ-(32)P]GTP to ADP to yield (γ-(32)P]ATP. Consequently, addition of ADP to a GTP-dependent protein-kinase assay resulted in a switch in the pattern of labeled products from that seen with GTP to that typically seen with ATP.
豌豆叶绿体中外膜囊泡蛋白激酶的鉴定
在豌豆叶绿体中外膜囊泡蛋白的制备中发现了一种鸟苷 5'-三磷酸（GTP）依赖性蛋白激酶。该蛋白激酶具有磷酸化几种囊泡膜蛋白的能力。主要的磷酸化产物是外膜的 23kDa 和 32.5kDa 蛋白。其他几种囊泡蛋白也有一定程度的标记。经酸水解标记蛋白后，大部分标记物被检测为磷酸丝氨酸，只有少量被检测为磷酸苏氨酸。使用了几个标准来区分存在于外膜中的 GTP 依赖性激酶和 ATP 依赖性激酶。ATP 依赖性激酶磷酸化了一组非常不同的囊泡膜蛋白。肝素抑制 GTP 依赖性激酶，但对 ATP 依赖性酶几乎没有影响。GTP 依赖性酶接受磷酸化卵白蛋白作为外部蛋白底物，而 ATP 依赖性酶则不能。叶绿体外膜还含有一种磷酸转移酶，能够将标记的磷酸从 [γ-(32)P]GTP 转移到 ADP 上，生成 (γ-(32)P]ATP。因此，在 GTP 依赖性蛋白激酶测定中加入 ADP 会导致标记产物的模式从 GTP 时的模式转变为通常的 ATP 模式。
