Two proteins function in the regulation of photosynthetic CO2 assimilation in chloroplasts
Two proteins function in the regulation of photosynthetic CO2 assimilation in chloroplasts
复制标题
两种蛋白质在叶绿体光合二氧化碳同化的调节中发挥作用
作者：
P. Schürmann;R. Wolosiuk;VICKI D. BREAZEALE;B. Buchanan
越来越多的证据表明，光合作用的光反应产物控制着参与叶绿体1-15吸收二氧化碳的酶的活性。在这些产物中，以光化学方式形成的还原剂似乎特别重要。这些还原剂包括还原形式的铁氧还蛋白2，6，10，一种强电负性叶绿体铁硫蛋白(E‘0=−0.42V)，它能激活两种关键的叶绿体酶果糖1，6-双磷酸酶和七糖L，7-双磷酸酶。这两种酶的激活除了需要还原的铁还蛋白外，还需要叶绿体固有的一种‘蛋白质因子’。为了阐明铁氧还蛋白相关酶激活的性质，我们将蛋白质因子分离成两个组分16：(1)部分纯化的蛋白质，暂时命名为“同化调节蛋白a”(ARPA)和(2)高纯度的无色团蛋白质，称为“同化调节蛋白b”(ARPB)。当还原的铁氧还蛋白被非生理的硫代试剂二硫苏糖醇6，10取代时，只需要后者来激活。
THERE is increasing evidence that products of the light reactions of photosynthesis govern the activity of enzymes involved in CO2 assimilation by chloroplasts1–15. Of these products, reductants formed photochemically seem to be of particular importance. Such reductants include the reduced form of ferredoxin2,6,10, a strongly electronegative chloroplast iron-sulphur protein (E′0=−0.42 V) that activates the two key chloroplast enzymes fructose 1,6-bis-phosphatase and sedoheptulose l,7-bis-phosphatase. Activation of both of these enzymes requires in addition to reduced ferredoxin a ‘protein factor’ that is indigenous to chloroplasts. In efforts to elucidate the nature of the ferredoxin-linked enzyme activation, we have separated the protein factor into two components16: (1) a partly purified protein, provisionally named “assimilation regulatory protein a” (ARPa) and (2) a highly purified chromophore-free protein called “assimilation regulatory protein b” (ARPb). Only the latter was required for activation when reduced ferredoxin was replaced by the non-physiological sulphydryl reagent dithiothreitol6,10.