Disruption of Ionic Interactions between the Nucleotide Binding Domain 1 (NBD1) and Middle (M) Domain in Hsp100 Disaggregase Unleashes Toxic Hyperactivity and Partial Independence from Hsp70
Disruption of Ionic Interactions between the Nucleotide Binding Domain 1 (NBD1) and Middle (M) Domain in Hsp100 Disaggregase Unleashes Toxic Hyperactivity and Partial Independence from Hsp70
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DOI：
10.1074/jbc.m112.387589
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发表时间：
2013-01-25
影响因子：
4.8
通讯作者：
Liberek, Krzysztof
中科院分区：
文献类型：
--
作者：
Lipinska, Natalia;Zietkiewicz, Szymon;Liberek, Krzysztof
Hsp100伴侣蛋白与Hsp70伴侣蛋白系统协同分解和重新激活热变性聚集蛋白，促进热应激后细胞存活。Hsp100解聚气体的同源性模型表明，在第一个核苷酸结合域（NBD1）和螺旋状中间亚域（解聚伴侣的特征域）之间存在一个保守的离子相互作用网络。旨在破坏酵母Hsp104和细菌ClpB分解气体中假定的离子相互作用的突变导致它们的生化特性发生显着变化。这些包括atp酶活性的增加，体外底物再生速率的显著增加，以及在分解过程中部分独立于Hsp70伴侣。矛盾的是，活性的增加导致了酵母和细菌细胞的严重生长障碍，而不是改善它们的耐热性。我们的研究结果表明，这种毒性活性是由于突变的分解气体能够独立于天然折叠蛋白Hsp70展开。在建议的网络中恢复特定盐桥的补充变化抑制了毒性作用。我们提出了一种新的Hsp100伴侣的结构方面，对分解反应的特异性和效率至关重要。
Hsp100 chaperones cooperate with the Hsp70 chaperone system to disaggregate and reactivate heat-denatured aggregated proteins to promote cell survival after heat stress. The homology models of Hsp100 disaggregases suggest the presence of a conserved network of ionic interactions between the first nucleotide binding domain (NBD1) and the coiled-coil middle subdomain, the signature domain of disaggregating chaperones. Mutations intended to disrupt the putative ionic interactions in yeast Hsp104 and bacterial ClpB disaggregases resulted in remarkable changes of their biochemical properties. These included an increase in ATPase activity, a significant increase in the rate of in vitro substrate renaturation, and partial independence from the Hsp70 chaperone in disaggregation. Paradoxically, the increased activities resulted in serious growth impediments in yeast and bacterial cells instead of improvement of their thermotolerance. Our results suggest that this toxic activity is due to the ability of the mutated disaggregases to unfold independently from Hsp70, native folded proteins. Complementary changes that restore particular salt bridges within the suggested network suppressed the toxic effects. We propose a novel structural aspect of Hsp100 chaperones crucial for specificity and efficiency of the disaggregation reaction.