Plasticity in eucaryotic 20S proteasome ring assembly revealed by a subunit deletion in yeast
Plasticity in eucaryotic 20S proteasome ring assembly revealed by a subunit deletion in yeast
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DOI：
10.1038/sj.emboj.7600059
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发表时间：
2004-02-11
期刊：
影响因子：
11.4
通讯作者：
Hochstrasser, M
中科院分区：
文献类型：
--
作者：
Velichutina, I;Connerly, PL;Hochstrasser, M
20S蛋白酶体由四个堆叠的七聚体环组成，在真核生物中，七聚体环由14个不同但相关的亚基组成。管理亚单位组装和放置的规则不被理解。我们发现，当Pre9/alpha3亚单位缺失时，酵母中会形成一种不同的蛋白酶体。纯化的Pre9 Delta蛋白酶体显示Pre6/Alpha4亚基的两倍丰富，这与每个外环中存在额外的Pre6拷贝一致。基于二硫化物工程和结构导向的抑制子分析，Pre6取代了Pre9通常占据的位置，这是一种依赖于亚单位间盐桥网络的替代。当拟南芥PAD1/alpha4在酵母中表达时，它不仅补充了pre6Delta和pre6Delta pre9Delta突变体，因此，植物alpha4亚基也可以在一个功能性酵母蛋白酶体中占据多个位置。重要的是，在前9Delta细胞中，蛋白酶体的生物发生在早期阶段被推迟，这表明在Alpha3位置掺入Pre9比Pre6更有利，从而促进了正确的组装。
The 20S proteasome is made up of four stacked heptameric rings, which in eucaryotes assemble from 14 different but related subunits. The rules governing subunit assembly and placement are not understood. We show that a different kind of proteasome forms in yeast when the Pre9/alpha3 subunit is deleted. Purified pre9Delta proteasomes show a two-fold enrichment for the Pre6/alpha4 subunit, consistent with the presence of an extra copy of Pre6 in each outer ring. Based on disulfide engineering and structure-guided suppressor analyses, Pre6 takes the position normally occupied by Pre9, a substitution that depends on a network of intersubunit salt bridges. When Arabidopsis PAD1/alpha4 is expressed in yeast, it complements not only pre6Delta but also pre6Delta pre9Delta mutants; therefore, the plant alpha4 subunit also can occupy multiple positions in a functional yeast proteasome. Importantly, biogenesis of proteasomes is delayed at an early stage in pre9Delta cells, suggesting an advantage for Pre9 over Pre6 incorporation at the alpha3 position that facilitates correct assembly.