Processing of small subunit precursor of ribulose bisphosphate carboxylase and its assembly into whole enzyme are stromal events
Processing of small subunit precursor of ribulose bisphosphate carboxylase and its assembly into whole enzyme are stromal events
复制标题
核酮糖二磷酸羧化酶小亚基前体的加工及其组装成整个酶是基质事件
作者：
Steven M. Smith;R. Ellis
叶绿体的发育需要细胞核和叶绿体遗传系统的活动，但它们各自的确切作用及其相互作用的机制尚不清楚。主要目标是确定每个叶绿体多肽的合成位点。对分离的亚细胞系统的研究，以及对完整细胞的抑制剂实验，已经证实许多叶绿体多肽是由细胞质核糖体产生的。这些多肽包括类囊体和基质多亚基蛋白的亚基。这些观察结果提出了两个问题：这些多肽是如何穿过叶绿体包膜的？它们在哪里组装成完整的功能性蛋白质？叶绿体酶二磷酸核酮糖羧化酶的小亚基作为高分子量多肽前体在细胞质中产生。我们在这里报道，这个前体的分裂和小亚基组装成整个二磷酸核酮糖羧化酶分子发生在叶绿体基质中。
CHLOROPLAST development requires the activities of both nuclear and chloroplast genetic systems, but the precise contribution of each and the mechanism by which they interact are not understood. A prime goal is to determine the site of synthesis of each chloroplast polypeptide. Studies with isolated subcellular systems, as well as inhibitor experiments with intact cells, have established that many chloroplast polypeptides are made by cytoplasmic ribosomes1. Such polypeptides include subunits of both thylakoid and stromal multi-subunit proteins. These observations raise two questions: how do these polypeptides traverse the chloroplast envelope, and where are they assembled into whole functional proteins? The small subunit of the chloroplast enzyme ribulose biphosphate carboxylase is made in the cytoplasm as a higher molecular weight polypeptide precursor2. We report here that the cleavage of this precursor and the assembly of the small subunit into whole ribulose bisphosphate carboxylase molecules takes place in the chloroplast stroma.