The long α-helix of SecA is important for the ATPase coupling of translocation
The long α-helix of SecA is important for the ATPase coupling of translocation
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DOI：
10.1074/jbc.m606906200
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发表时间：
2006-11-24
影响因子：
4.8
通讯作者：
Ito, Koreaki
中科院分区：
文献类型：
--
作者：
Mori, Hiroyuki;Ito, Koreaki
SecA含有两个ATP酶折叠（NBF 1和NBF 2）和其他相互作用/调节结构域，所有这些结构域都通过沿分子沿着的长螺旋支架结构域（HSD）连接。在这里，我们确定了一个功能上重要的和空间上相邻的SecA残基对，Arg-642上的HSD和Glu-400上的NBF 1。在任一位置的电荷反转取代以及这些位置的二硫键束缚使易位活性失活。然而，有趣的是，转位失活的SecA变体完全保留了响应于前蛋白和SecYEG转位子而上调ATP酶的能力。在NBF 2和HSD的铰链形成边界处的第二位点改变可抑制易位缺陷。基于这些结果，我们提出SecA的运动功能是通过配体激活的ATP酶引擎及其在HSD-mediated转化为前蛋白转位的机械功来实现的。
SecA contains two ATPase folds (NBF1 and NBF2) and other interaction/regulatory domains, all of which are connected by a long helical scaffold domain (HSD) running along the molecule. Here we identified a functionally important and spatially adjacent pair of SecA residues, Arg-642 on HSD and Glu-400 on NBF1. A charge-reversing substitution at either position as well as disulfide tethering of these positions inactivated the translocation activity. Interestingly, however, the translocation-inactive SecA variants fully retained the ability to up-regulate the ATPase in response to a preprotein and the SecYEG translocon. The translocation defect was suppressible by second site alterations at the hinge-forming boundary of NBF2 and HSD. Based on these results, we propose that the motor function of SecA is realized by ligand-activated ATPase engine and its HSD-mediated conversion into the mechanical work of preprotein translocation.