Laboratoire de Physiologie Cellulaire Végétale, CNRS ERA 488, Université de Grenoble I, BP 68, F-38402, Saint Martin d'Hères Cedex, France.
Plant Mol Biol. 1984 Mar;3(2):83-90. doi: 10.1007/BF00040032.
Chloroplast ribosomal proteins from spinach have been prepared in the presence of a protease inhibitor and some modifications have been introduced to the previous characterization of the 50S subunits (Mache et al., MGG, 177, 333, 1980): 33 ribosomal proteins are detected instead of 34. No change has been observed for the 30S subunits.Using a light-driven system of protein synthesis it is shown that up to ten ribosomal proteins of the 30S and eight proteins of the 50S subunits are made in the chloroplast.Newly synthesized ribosomal subunits have been analysed on CsCl gradients after sedimentation at equilibrium, allowing the separation of fully assembled subunits from incomplete ribosomal particles. Most of the newly made 50S subunits are fully assembled (ρ=1.634). A small amount of incomplete 50S particles (ρ=1.686) is detectable. Newly made 30S subunits (ρ=1.598) and incomplete 30S particles (ρ=1.691) are also observed. The ribosomal proteins of the incomplete 30S have been determined. They contain eight or nine of the 30S-proteins, seven of which are synthesized within the chloroplast. It is suggested that incomplete ribosomal particles resulted from a step in the assembly of ribosomal subunits.
菠菜叶绿体核糖体蛋白在蛋白酶抑制剂存在的情况下被制备，并对以前对 50S 亚基的特征描述进行了一些修改（Mache 等人，MGG，177，333，1980）：检测到 33 个核糖体蛋白，而不是 34 个。30S 亚基没有观察到变化。
使用光驱动的蛋白质合成系统表明，叶绿体中可以合成多达 10 个 30S 核糖体蛋白和 8 个 50S 亚基蛋白。
在平衡沉淀后，CsCl 梯度上分析新合成的核糖体亚基，允许将完全组装的亚基与不完全核糖体颗粒分离。大多数新合成的 50S 亚基是完全组装的（ρ=1.634）。可以检测到少量不完全的 50S 颗粒（ρ=1.686）。还观察到新合成的 30S 亚基（ρ=1.598）和不完全的 30S 颗粒（ρ=1.691）。已确定不完全 30S 颗粒中的核糖体蛋白。它们含有 30S 蛋白中的 8 或 9 个，其中 7 个在叶绿体中合成。
据推测，不完全核糖体颗粒是核糖体亚基组装过程中的一个步骤造成的。
