Two Independent Mechanisms Down-regulate the Intrinsic SecA ATPase Activity*
Two Independent Mechanisms Down-regulate the Intrinsic SecA ATPase Activity*
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两种独立的机制下调内在 SecA ATP 酶活性*
DOI：
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发表时间：
2000
影响因子：
4.8
通讯作者：
Koreaki Ito
中科院分区：
文献类型：
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作者：
H. Nakatogawa;H. Mori;Koreaki Ito
SecA通过与ATP、前蛋白和SecYEG膜组分相互作用启动蛋白质易位。在这样的条件下，它经历了一个构象变化，其特征在于膜插入，然后是ATP的水解，使前蛋白的释放和SecA本身的脱插入用于下一个反应循环。在没有进行易位的情况下，SecA的ATP酶活性保持非常低。以前，它表明，C-末端34 kDa的SecA结构域与N-末端68 kDa的ATP酶结构域相互作用，下调ATP酶。在这里，我们表明，使用一个放松管制SecA突变体，固有的ATP酶活性受到双重抑制机制。因此，所提出的第二ATP结合结构域下调由初级ATP酶结构域执行的ATP酶活性。这种调节，在N-末端ATP酶结构域，运作独立的C-末端结构域介导的调节。这两种机制的情况下，在一个50倍的升高易位解偶联ATP水解。
SecA initiates protein translocation by interacting with ATP, preprotein, and the SecYEG membrane components. Under such conditions, it undergoes a conformational change characterized as membrane insertion, which is then followed by hydrolysis of ATP, enabling the release of the preprotein and deinsertion of SecA itself for the next cycle of reactions. Without ongoing translocation, the ATPase activity of SecA is kept very low. Previously, it was shown that the C-terminal 34-kDa domain of SecA interacts with the N-terminal 68-kDa ATPase domain to down-regulate the ATPase. Here, we show, using a deregulated SecA mutant, that the intrinsic ATPase activity is subject to dual inhibitory mechanisms. Thus, the proposed second ATP-binding domain down-regulates the ATPase activity executed by the primary ATPase domain. This regulation, within the N-terminal ATPase domain, operates independently of the C-terminal domain-mediated regulation. The absence of both the mechanisms resulted in a 50-fold elevation of translocation-uncoupled ATP hydrolysis.