Diverse pore loops of the AAA plus ClpX machine mediate unassisted and adaptor-dependent recognition of ssrA-tagged substrates
Diverse pore loops of the AAA plus ClpX machine mediate unassisted and adaptor-dependent recognition of ssrA-tagged substrates
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DOI：
10.1016/j.molcel.2008.02.002
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发表时间：
2008-02-29
期刊：
影响因子：
16
通讯作者：
Sauer, Robert T.
中科院分区：
文献类型：
--
作者：
Martin, Andreas;Baker, Tania A.;Sauer, Robert T.
ClpX是一种典型的蛋白水解性AAA+解折叠酶，在依赖于ATP的解折叠和将变性多肽转移到ClpP中进行降解之前，必须结合适当底物的SSrA标记。在这里，特异性移植和二硫键交联实验表明，ssrA标签与形成ClpX六聚体中央通道的上、中、下部分的不同环相互作用。我们的结果支持两步结合机制，其中顶部环作为特异性过滤器，其余环形成多肽标签在毛孔内相对较深的结合部位。交联实验表明，六角体中的孔环是交错排列的，孔环构象中的变化依赖于核苷酸。这种初始标签结合的机制将允许一个或多个孔环中依赖于ATIP的构象变化，以驱动多肽移位，强制展开，并通过ClpX孔中介变性蛋白质的穿线。
ClpX, an archetypal proteolytic AAA+ unfoldase, must engage the ssrA tags of appropriate substrates prior to ATP-dependent unfolding and translocation of the denatured polypeptide into ClpP for degradation. Here, specificity-transplant and disulfide-crosslinking experiments reveal that the ssrA tag interacts with different loops that form the top, middle, and lower portions of the central channel of the ClpX hexamer. Our results support a two-step binding mechanism, in which the top loop serves as a specificity filter and the remaining loops form a binding site for the peptide tag relatively deep within the pore. Crosslinking experiments suggest a staggered arrangement of pore loops in the hexamer and nucleotide-dependent changes in pore-loop conformations. This mechanism of initial tag binding would allow ATIP-dependent conformational changes in one or more pore loops to drive peptide translocation, force unfolding, and mediate threading of the denatured protein through the ClpX pore.