Giese K, Subramanian A R
Max-Planck-Institut für Molekulare Genetik, Abteilung Wittmann, Berlin, Germany.
FEBS Lett. 1991 Aug 19;288(1-2):72-6. doi: 10.1016/0014-5793(91)81005-s.
Chloroplast ribosomal protein L13 is encoded in the plant nucleus and is considerably larger than its eubacterial homologue by having NH2- and COOH-terminal extensions with no homology to any known sequences (Phua et al., J Biol. Chem. 264, 1968-1971, 1989). We made two gene constructs of L13 cDNA using the polymerase chain reaction (PCR) and expressed them in Escherichia coli. Analysis of the ribosomes and polysomes from these cells, using an antiserum specific to chloroplast L13, shows that the expressed proteins are incorporated, in the presence of the homologous E. coli L13, into functional ribosomes which participate in protein synthesis (i.e. polysomes). Evidence is obtained that the large NH2-terminal extension probably lies on the surface of these 'mosaic ribosomes.' This first report of the assembly into E. coli ribosomes of nuclear-coded chloroplast ribosomal protein with terminal extensions thus suggest an extraordinary conservation in the function of eubacterial type ribosomal proteins, despite the many changes in protein structure during their evolution inside a eukaryotic system.
叶绿体核糖体蛋白L13在植物细胞核中编码，并且由于具有与任何已知序列均无同源性的NH2-末端和COOH-末端延伸，其比真细菌同源物大得多（Phua等人，《生物化学杂志》264, 1968 - 1971, 1989）。我们使用聚合酶链反应（PCR）构建了两个L13 cDNA基因构建体，并在大肠杆菌中进行表达。使用针对叶绿体L13的抗血清对这些细胞的核糖体和多核糖体进行分析，结果表明，在同源大肠杆菌L13存在的情况下，所表达的蛋白质被整合到参与蛋白质合成的功能性核糖体（即多核糖体）中。有证据表明，较大的NH2-末端延伸可能位于这些“嵌合核糖体”的表面。核编码的带有末端延伸的叶绿体核糖体蛋白组装到大肠杆菌核糖体中的这一首次报道表明，尽管真细菌型核糖体蛋白在真核系统内进化过程中蛋白质结构发生了许多变化，但其功能具有非凡的保守性。
