Studies on structure and the biological functions of a large multi-molecular complex "the proteasome"

大型多分子复合物“蛋白酶体”的结构和生物学功能研究

基本信息

批准号：
03102006
负责人：
ICHIHARA Akira
金额：
$ 108.8万
依托单位：
Institute for Enzyme Research, The University of Tokushima
依托单位国家：
日本
项目类别：
Grant-in-Aid for Specially Promoted Research
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

项目摘要

(1) Structural Analysis of Proteasomes at the Molecular Level : We demonstrated that proteasomes are found as two isoforms in cells. One is the ATP-independent 20S form and the other is an ATP-dependent 26S form. Various physical analyzes showed that molecular masses of these two forms are determined to be approximately 750 kDa and 2000 kDa, respectively. The primary structures of 7 alpha-type and 9 beta-type subunits of the 20S proteasome complex in human, rat and yeast were determined by their cDNA cloning. Based on the homology analysis, we proposed the novel term "the proteasome gene family" for these highly homologous gene groups. Furthermore, we have prepared the large crystals of the bovine 20S proteasome and carried out its preliminary X-ray analysis. By electron microscopy, we proposed the "caterpillar-shape" model for the 26S proteasome, consisting of approximately 50 non-identical subunits. The 26S proteasome was found to be the unusually large supra-molecular complex.(2) Molecular Functions of Proteasomes : The 26S proteasome was demonstrated to be an ATP-dependent protease catalyzing selective degradation of target proteins conjugated with multiple ubiquitins as the degradation signal. Moreover, we found for the first time that ornithine decarboxylase, a most short-lived enzyme in cells responsible for biosynthesis of polyamines, was degraded ATP-dependently by the 26S proteasome without ubiquitination.(3) Physiological Functions of Proteasomes : The 26S proteasome degraded various nuclear oncoproteins, such as Mos, Fos and Myc, closely related with cell cycle progression in an ATP-, ubiquitin-dependent fashion, suggesting possible involvement of the proteasome in cell cycle regulation. In addition, we found that gamma-interferon induced proteasomes with different subunit organizations for acquirement of the functional diversity and suggested that proteasoms play an essential role for the MHC class-I restricted antigen processing pathway.

（1）分子水平上蛋白酶体的结构分析：我们证明蛋白酶体在细胞中被发现是两个同工型。一种是独立于ATP的20S形式，另一种是ATP依赖的26S形式。各种物理分析表明，这两种形式的分子质量分别确定为约750 kDa和2000 kDa。 7种α型和9个β型亚基的主要结构在人，大鼠和酵母中的蛋白酶体复合物的主要结构是通过其cDNA克隆确定的。基于同源性分析，我们提出了这些高度同源基因组的新术语“蛋白酶体基因家族”。此外，我们已经准备了牛20S蛋白酶体的大晶体，并进行了初步的X射线分析。通过电子显微镜，我们提出了26S蛋白酶体的“毛毛虫形状”模型，其中约50个非相同的亚基。发现26S蛋白酶体是异常大的上分子复合物。（2）蛋白酶体的分子功能：26S蛋白酶体被证明是ATP依赖性蛋白酶催化靶向靶蛋白的选择性降解，靶蛋白与多种泛素相结合，作为降解信号。 Moreover, we found for the first time that ornithine decarboxylase, a most short-lived enzyme in cells responsible for biosynthesis of polyamines, was degraded ATP-dependently by the 26S proteasome without ubiquitination.(3) Physiological Functions of Proteasomes : The 26S proteasome degraded various nuclear oncoproteins, such as Mos, Fos and Myc, closely related with cell cycle progression以ATP-泛素依赖性方式，表明蛋白酶体可能参与细胞周期调节。此外，我们发现γ-互化引起与不同亚基组织的蛋白酶体以获取功能多样性，并建议蛋白酶对MHC I类限制的抗原处理途径起着至关重要的作用。