Conformational Changes of the Clamp of the Protein Translocation ATPase SecA.
Conformational Changes of the Clamp of the Protein Translocation ATPase SecA.
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DOI：
10.1016/j.jmb.2015.05.003
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发表时间：
2015-07-17
影响因子：
5.6
通讯作者：
Gumbart, James C.
中科院分区：
文献类型：
--
作者：
Chen, Yu;Bauer, Benedikt W.;Rapoport, Tom A.;Gumbart, James C.
翻译后的蛋白质跨细菌质膜的转运是由SecA ATPase和蛋白质传导的SecY通道相互作用所介导的。SECA由多个结构域组成，包括两个核苷酸结合区(Nbd1和Nbd2)、多肽交联区(PPXD)、螺旋支架结构域(HSD)和螺旋翼区(HWD)。PPXD、HSD和Nbd2形成一个夹具，将多肽底物定位在通道上方，从而可以通过HSD的两个螺旋手指将其推入通道。在移位过程中，底物是如何容纳在夹子中的还不清楚。在此，我们报道了松毛虫T.maritima Seca的晶体结构，其分辨率为1.9。结构分析和自由能计算表明，这种新结构代表了夹子从开放构象向闭合构象转变的中间状态。分子动力学模拟表明，钳子的关闭分两个阶段发生，PPXD、HSD和HWD作为一个单元最初移动，然后PPXD单独向Nbd2移动。在多肽链存在下的模拟表明，底物通过动态氢键与钳的背面结合，并且钳被PPXD的保守环横向闭合。钳夹打开或关闭的突变破坏取消了蛋白质易位。这些结果表明，在蛋白质转运过程中，SecA的构象变化如何允许底物结合和移动。
Post-translational protein translocation across the bacterial plasma membrane is mediated by the interplay of the SecA ATPase and the protein-conducting SecY channel. SecA consists of several domains, including two nucleotide-binding domains (NBD1 and NBD2), a polypeptide crosslinking domain (PPXD), a helical scaffold domain (HSD), and a helical wing domain (HWD). PPXD, HSD, and NBD2 form a clamp that positions the polypeptide substrate above the channel, so that it can be pushed into the channel by a two-helix finger of the HSD. How the substrate is accommodated in the clamp during translocation is unclear. Here, we report a crystal structure of T. maritima SecA at 1.9 Å resolution. Structural analysis and free energy calculations indicate that the new structure represents an intermediate state during the transition of the clamp from an open to a closed conformation. Molecular dynamics simulations show that closure of the clamp occurs in two phases, an initial movement of PPXD, HSD, and HWD as a unit, followed by a movement of PPXD alone towards NBD2. Simulations in the presence of a polypeptide chain show that the substrate associates with the back of the clamp by dynamic hydrogen bonding, and that the clamp is laterally closed by a conserved loop of the PPXD. Mutational disruption of clamp opening or closure abolishes protein translocation. These results suggest how conformational changes of SecA allow substrate binding and movement during protein translocation.
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影响因子：
64.5
作者：
ECONOMOU, A;WICKNER, W
通讯作者：
WICKNER, W
影响因子：
15
作者：
Kim, Dorothy M.;Zheng, Haiyan;Hunt, John F.
通讯作者：
Hunt, John F.
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
5.6
作者：
Papanikolau, Yannis;Papadovasilaki, Maria;Petratos, Kyriacos
通讯作者：
Petratos, Kyriacos
影响因子：
5.5
作者：
Best, Robert B.;Zhu, Xiao;Shim, Jihyun;Lopes, Pedro E. M.;Mittal, Jeetain;Feig, Michael;MacKerell, Alexander D., Jr.
通讯作者：
MacKerell, Alexander D., Jr.