Heptameric ring structure of the heat-shock protein ClpB, a protein-activated ATPase in Escherichia coli
Heptameric ring structure of the heat-shock protein ClpB, a protein-activated ATPase in Escherichia coli
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DOI：
10.1006/jmbi.2000.4165
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发表时间：
2000-11-10
影响因子：
5.6
通讯作者：
Chung, CH
中科院分区：
文献类型：
--
作者：
Kim, KI;Cheong, GW;Chung, CH
热休克蛋白ClpB是一种蛋白质激活的ATP酶，是大肠杆菌在高温下生存所必需的。ClpB最近也被认为在聚集蛋白的再活化中起伴侣的作用。此外，clpB基因已被证明含有两个翻译起始位点，因此编码两种不同大小的多肽。为了确定ClpB的结构组织，ClpB蛋白进行化学交联分析和电子显微镜。ClpB蛋白质的平均图像与端对取向揭示了一个七元，环形结构与中央腔。他们的侧视图显示了一个两层结构，在复合体的赤道平面上质量均匀分布。由于ClpB亚基具有两个包含核苷酸结合的共有序列的大区域，ClpB七聚体的每一层似乎代表排列在环上的主要结构域之一的侧投影。在不存在盐和ATP的情况下，ClpB蛋白显示出形成七聚体的高趋势。然而，它们解离成各种具有较小尺寸的低聚物，这取决于盐浓度。在0.2 M NaCl以上，ClpB蛋白在不存在ATP的情况下最有可能表现为单体，但在其存在下组装成七聚体。此外，第一个ATP结合位点的突变，但不是第二个位点，防止在0.3 M NaCl的存在下的ClpB蛋白的ATP依赖性寡聚化。这些结果表明，ClpB有一个七聚体的环形结构，中央空腔，这种结构的组织需要Am结合到第一个核苷酸结合位点定位到N-末端的一半的ATP酶。(C)北京大学出版社.
The heat-shock protein ClpB is a protein-activated ATPase that is essential for survival of Escherichia coli at high temperatures. ClpB has also recently been suggested to function as a chaperone in reactivation of aggregated proteins. In addition, the clpB gene has been shown to contain two translational initiation sites and therefore encode two polypeptides of different size. To determine the structural organization of ClpB, the ClpB proteins were subjected to chemical cross-linking analysis and electron microscopy. The average images of the ClpB proteins with end on orientation revealed a seven-membered, ring-shaped structure with a central cavity. Their side-on view showed a two-layered structure with an equal distribution of mass across the equatorial plane of the complex. Since the ClpB subunit has two large regions containing consensus sequences for nucleotide binding, each layer of the ClpB heptamer appears to represent the side projection of one of the major domains arranged on a ring. Ln the absence of salt and ATP, the ClpB proteins showed a high tendency to form a heptamer. However, they dissociated into various species of oligomers with smaller sizes, depending on salt concentration. Above 0.2 M NaCl, the ClpB proteins behaved most likely as a monomer in the absence of ATP, but assembled into a heptamer in its presence. Furthermore, mutations of the first ATP-binding site, but not the second site, prevented the ATP-dependent oligomerization of the ClpB proteins in the presence of 0.3 M NaCl. These results indicate that ClpB has a heptameric ring-shaped structure with a central cavity and this structural organization requires Am binding to the first nucleotide-binding site localized to the N-terminal half of the ATPase. (C) 2000 Academic Press.