Molecular structure of 20S and 26S proteasomes.

Enzyme & protein Pub Date : 1993-01-01 DOI:10.1159/000468683
N Tanahashi, C Tsurumi, T Tamura, K Tanaka
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引用次数: 76

Abstract

Eukaryotic proteasomes are unusually large protein complexes with characteristic sets of subunits and have been classified into two isoforms with apparent sedimentation coefficients of 20S and 26S, respectively. The 20S proteasome (previously named the multicatalytic proteinase complex) is a cylindrical particle with a molecular weight (MW) of approximately 750 kD. It is a dimeric assembly of two symmetrical discs, each consisting of 7 alpha-type subunits and 7 beta-type subunits, having the molecular organization alpha n[1-7)beta n[1-7)beta n[1-7)alpha n[1-7), where 'n' indicates the number of heterogeneous 7 subunits with MWs of 21-32 kD. The alpha-type and beta-type subunits constitute a unique multi-gene family encoding previously unidentified, but homologous, polypeptides that have been conserved during evolution. Interestingly, some beta-type subunits with catalytic functions appear to be replaced by very homologous, but distinct, gene products that might be generated by gene duplication in response to extracellular signals, such as gamma-interferon, suggesting that the 20S proteasome exists in cells as a heterogeneous population with functional diversity. The 26S proteasome is a eukaryotic ATP-dependent protease, selectively degrading various cellular proteins with specific degradation signals such as a multi-ubiquitin chain. It is a cylindrical caterpillar-shaped complex with a MW of about 2,000 kD. The 26S proteasome is a symmetrical assembly of a central 20S proteasome and a large terminal polypeptide complex with an apparent sedimentation coefficient of 22S. The terminal 22S subset consists of multiple components with MWs of 30-110 kD, which possibly have regulatory functions, and contains multiple ATPases, a de-ubiquitinating enzyme and the recognition molecule(s) for the target proteins. Thus the 26S proteasome is a multi-molecular assembly, consisting of the 20S proteasome and the 22S regulatory subunit complex.

20S和26S蛋白酶体的分子结构。
真核蛋白酶体是一种异常大的蛋白质复合物,具有特征性的亚基集合,并被分为两种亚型,其表观沉降系数分别为20S和26S。20S蛋白酶体(以前称为多催化蛋白酶复合物)是一种圆柱形颗粒,分子量(MW)约为750 kD。它是由两个对称圆盘组成的二聚体,每个圆盘由7个α型亚基和7个β型亚基组成,其分子组织为α n[1-7] β n[1-7] β n[1-7] α n[1-7],其中“n”表示分子量为21-32 kD的异构亚基的数量。α -型和β -型亚基构成了一个独特的多基因家族,编码以前未发现的,但同源的,在进化过程中保守的多肽。有趣的是,一些具有催化功能的β型亚基似乎被非常同源但不同的基因产物所取代,这些基因产物可能是由基因复制响应细胞外信号(如γ -干扰素)产生的,这表明20S蛋白酶体在细胞中作为一个具有功能多样性的异质群体存在。26S蛋白酶体是一种真核生物atp依赖性蛋白酶,具有选择性地降解多种细胞蛋白的特异性降解信号,如多泛素链。它是一个圆柱形的毛虫状复合物,分子量约为2,000 kD。26S蛋白酶体是一个中心20S蛋白酶体和一个大的末端多肽复合物的对称组装,其表观沉降系数为22S。末端22S亚群由分子量为30-110 kD的多个组分组成,可能具有调控功能,并包含多个atp酶、一个去泛素化酶和靶蛋白的识别分子。因此,26S蛋白酶体是一个多分子组装体,由20S蛋白酶体和22S调节亚基复合物组成。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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