Two-Step Activation Mechanism of the ClpB Disaggregase for Sequential Substrate Threading by the Main ATPase Motor
Two-Step Activation Mechanism of the ClpB Disaggregase for Sequential Substrate Threading by the Main ATPase Motor
复制标题
DOI：
10.1016/j.celrep.2019.05.075
复制
发表时间：
2019-06-18
期刊：
影响因子：
8.8
通讯作者：
Saibil, Helen R.
中科院分区：
文献类型：
--
作者：
Deville, Celia;Franke, Kamila;Saibil, Helen R.
AAA+蛋白形成水解ATP的不对称六聚体环，并通过移动的底物结合孔环将底物蛋白穿过中央通道。了解ATP酶和线程活动如何调节和交织是理解AAA+蛋白机制的关键。我们研究了解聚酶ClpB，它含有串联的ATP酶结构域（AAA 1，AAA 2）和低和高ATP酶和线程活动之间的转变。卷曲螺旋M结构域通过环绕AAA 1环抑制ClpB活性。在这里，我们确定的ClpB激活的机制，通过比较ATP酶的机制和cryo-EM结构的ClpB野生型和组成型活性ClpB M-结构域突变体。我们发现，ClpB激活降低ATP酶的协同性，并诱导ATP水解的AAA 2环，主要的ATP酶马达的顺序模式。AAA 1和AAA 2环不同步工作，而是交替循环工作。这确保了高抓地力，使基板线程通过一个渐进的，绳索攀登机制。
AAA+ proteins form asymmetric hexameric rings that hydrolyze ATP and thread substrate proteins through a central channel via mobile substrate-binding pore loops. Understanding how ATPase and threading activities are regulated and intertwined is key to understanding the AAA+ protein mechanism. We studied the disaggregase ClpB, which contains tandem ATPase domains (AAA1, AAA2) and shifts between low and high ATPase and threading activities. Coiled-coil M-domains repress ClpB activity by encircling the AAA1 ring. Here, we determine the mechanism of ClpB activation by comparing ATPase mechanisms and cryo-EM structures of ClpB wild-type and a constitutively active ClpB M-domain mutant. We show that ClpB activation reduces ATPase cooperativity and induces a sequential mode of ATP hydrolysis in the AAA2 ring, the main ATPase motor. AAA1 and AAA2 rings do not work synchronously but in alternating cycles. This ensures high grip, enabling substrate threading via a processive, rope-climbing mechanism.