Structural Basis for Specific Recognition of Rpt1p, an ATPase Subunit of 26 S Proteasome, by Proteasome-dedicated Chaperone Hsm3p
Structural Basis for Specific Recognition of Rpt1p, an ATPase Subunit of 26 S Proteasome, by Proteasome-dedicated Chaperone Hsm3p
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DOI：
10.1074/jbc.m112.345876
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发表时间：
2012-04-06
影响因子：
4.8
通讯作者：
Mizushima, Tsunehiro
中科院分区：
文献类型：
--
作者：
Takagi, Kenji;Kim, Sangwoo;Mizushima, Tsunehiro
26 S蛋白酶体是一种分子量为2.5-MDa的分子机器，在真核细胞中降解泛素化蛋白。它由一个蛋白水解核心颗粒和两个19 S调节颗粒（RPs）组成，RPs由6个ATP酶（Rpt）和13个非ATP酶（Rpn）亚基组成。多个蛋白酶体专用分子伴侣促进蛋白酶体的组装，但对其详细机制知之甚少。Hsm 3是19 S RP的一种分子伴侣，在ATP酶环成熟过程中与Rpt 1亚基的C端结构域短暂结合，形成Hsm 3-Rpt 1-Rpt 2-Rpn 1四聚体复合物。为了阐明Hsm 3功能的结构基础，我们确定了Hsm 3及其与Rpt 1亚基的C-末端结构域（Rpt 1C）的复合物的晶体结构。Hsm 3具有由11个HEAT重复序列组成的C形结构。Hsm 3-Rpt 1C复合物的结构表明，Hsm 3和Rpt 1之间的相互作用表面是一个疏水的核心和互补的带电表面。Hsm 3-Rpt 1表面的突变导致26 S蛋白酶体的组装缺陷。此外，Hsm 3-Rpt环复合物的结构模型和体外结合试验表明，Hsm 3可以结合Rpt 2，除了Rpt 1。总的来说，我们的研究结果提供了结构基础的分子功能的Hsm 3的RP组装。
The 26 S proteasome is a 2.5-MDa molecular machine that degrades ubiquitinated proteins in eukaryotic cells. It consists of a proteolytic core particle and two 19 S regulatory particles (RPs) composed of 6 ATPase (Rpt) and 13 non-ATPase (Rpn) subunits. Multiple proteasome-dedicated chaperones facilitate the assembly of the proteasome, but little is known about the detailed mechanisms. Hsm3, a 19 S RP dedicated chaperone, transiently binds to the C-terminal domain of the Rpt1 subunit and forms a tetrameric complex, Hsm3-Rpt1-Rpt2-Rpn1, during maturation of the ATPase ring of 19 S RP. To elucidate the structural basis of Hsm3 function, we determined the crystal structures of Hsm3 and its complex with the C-terminal domain of the Rpt1 subunit (Rpt1C). Hsm3 has a C-shaped structure that consists of 11 HEAT repeats. The structure of the Hsm3-Rpt1C complex revealed that the interacting surface between Hsm3 and Rpt1 is a hydrophobic core and a complementary charged surface. Mutations in the Hsm3-Rpt1 surface resulted in the assembly defect of the 26 S proteasome. Furthermore, a structural model of the Hsm3-Rpt ring complex and an in vitro binding assay suggest that Hsm3 can bind Rpt2 in addition to Rpt1. Collectively, our results provide the structural basis of the molecular functions of Hsm3 for the RP assembly.