The structures of HsIU and ATP-dependent protease HsIU-HsIV
The structures of HsIU and ATP-dependent protease HsIU-HsIV
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DOI：
10.1038/35001629
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发表时间：
2000-02-17
期刊：
影响因子：
64.8
通讯作者：
Huber, R
中科院分区：
文献类型：
--
作者：
Bochtler, M;Hartmann, C;Huber, R
细胞质蛋白质的降解是一个ATP依赖性过程。底物靶向真核生物中的单一可溶性蛋白酶，26 S蛋白酶体（2，3）和原核生物中的许多不相关的蛋白酶（4，5）。随着在大肠杆菌中发现ATP依赖性蛋白酶HslVU（热休克位点VU）（6-8），出现了令人惊讶的联系。其蛋白酶组分HsIV与20 S蛋白酶体β亚基具有相似的20%序列相似性（6）和保守的折叠（9）。HslU是ATP酶的Hsp 100（Clp）家族的成员。在这里，我们报告的晶体结构的游离HslU和820，000相对分子质量的复合物HslU和HslV的第一个结构的一套完整的组件的ATP依赖性蛋白酶。HslV和HslU显示六重对称性，排除了需要两个组分之间对称性错配的蛋白酶活化机制。相反，在HslU中存在构象柔性和结构域运动，在HslV中存在局部有序-无序转变。HslU的单个亚基含有两个相对取向的球状结构域，其与核苷酸结合和未结合状态相关。它们与N-乙基马来酰亚胺敏感性融合蛋白（AAA-ATPase的原型）中的对应物惊人地相似（10，11）。HslU中的第三个主要是α-螺旋结构域介导与HslV的接触，并且可能是蛋白酶体AAA-ATP酶中氨基末端结构域的结构等价物。
The degradation of cytoplasmic proteins is an ATP-dependent process'. Substrates are targeted to a single soluble protease, the 26S proteasome(2,3), in eukaryotes and to a number of unrelated proteases in prokaryotes(4,5). A surprising Link emerged with the discovery of the ATP-dependent protease HslVU (heat shock locus VU)(6-8) in Escherichia coli. Its protease component HsIV shares similar to 20% sequence similarity(6) and a conserved fold(9) with 20S proteasome beta-subunits. HslU is a member of the Hsp100 (Clp) family of ATPases. Here we report the crystal structures of free HslU and an 820,000 relative molecular mass complex of HslU and HslV-the first structure of a complete set of components of an ATP-dependent protease. HslV and HslU display sixfold symmetry, ruling out mechanisms of protease activation that require a symmetry mismatch between the two components. Instead, there is conformational flexibility and domain motion in HslU and a localized order-disorder transition in HslV. Individual subunits of HslU contain two globular domains in relative orientations that correlate with nucleotide bound and unbound states. They are surprisingly similar to their counterparts in N-ethylmaleimide-sensitive fusion protein(10,11), the prototype of an AAA-ATPase. A third, mostly a-helical domain in HslU mediates the contact with HslV and may be the structural equivalent of the amino-terminal domains in proteasomal AAA-ATPases.