Functional analysis of ribosomes from eukaryotes possessing prokaryotic robosomes.

长期以来，人们一直认为原核和真核核糖体在功能和结构上存在着离散的差异。这些事实影响了真核生物是两种原核细胞融合而产生的概念。近年来，有报道称某些寄生过程具有与原核核糖体相似的沉降系数的核糖体。本项目旨在通过分析真核生物中原核核糖体的功能来阐明真核生物的起源。以核糖体沉降系数为70S的小孢子虫为原料制备核糖体组分和其他可溶性酶组分。同时制备大鼠肝脏核糖体和大肠杆菌核糖体进行比较。在ATP再生系统中，大肠杆菌和大鼠肝脏的核糖体根据外源添加的聚(U)被积极地结合标记苯丙氨酸。然而，来自家蚕的核糖体，在任何被检查的系统中，即使有，也很少含有标记氨基酸。细胞破坏或细胞分离方法的改变未能改善系统的活性。我们现在得出的结论是，这种材料，即休眠的蚕蛾孢子，不适合作为生物活性核糖体的来源。在研究过程中，我们从家蚕基因组中克隆了包括hsp70基因在内的一些基因。序列分析表明，在生物进化过程中，不具有线粒体的n.b ombycis继发性地丢失了线粒体。

It has long been believed that there are discrete differences between prokaryotic and eukaryotic ribosomes in both function and structure. These facts have influenced on the concept that eukaryotes emerged as a result of fusion of two kinds of prokaryotic cells. Recently, it has been reported that some parasitic procysts possessed ribosomes with sedimentation coefficient similar to prokaryotic ribosomes. This project aimed to elucidate the origin of eukaryote by analyzing the function of the prokaryotic ribosomes from the eukaryotes.Ribosomal fraction and other soluble enzyme fractions were prepared from microsporidia Nosema bombycis whose ribosome has a sedimentation coefficient of 70S.Ribosomes from rat liver and Escherichia coli were also prepared for comparison.With ATP regeneration system, ribosomes from E.coli and rat liver were actively incorporatelabeled phenylalanine depending exogenously added poly(U).Ribosomes from N.bombycis, however, incorporated little, if any, labeled amino acids in any of the system examined.Alteration of cell disrupting or cell fractionation methods failed to improve the activity of the system. We now conclude that the material, i. e., dormant spores of N.bombycis, is not suitable for the source of biologically active ribosomes.During the course of this study, we cloned some genes including HSP7O gene from N.bombycis genome. The sequence analysis revealed that N.bom bycis which does not have mito-chondria lost mitochondria secondarily during the evolution of the organism.