Structure of the substrate-engaged SecA-SecY protein translocation machine
Structure of the substrate-engaged SecA-SecY protein translocation machine
复制标题
底物结合的 SecA-SecY 蛋白易位机的结构
DOI：
10.1038/s41467-019-10918-2
复制
发表时间：
2019-06-28
影响因子：
16.6
通讯作者：
Li，Long
中科院分区：
文献类型：
--
作者：
Ma，Chengying;Wu，Xiaofei;Li，Long
Sec 61/SecY通道允许许多蛋白质跨真核内质网膜或原核质膜易位。在细菌中，大多数分泌性蛋白质通过SecA ATP酶通过SecY通道进行后期转运。由于缺乏结构信息，多肽如何通过SecA-SecY复合物移动还知之甚少。在这里，我们报告了一个电子冷冻显微镜（冷冻EM）结构的易位SecA-SecY复杂的脂质环境。可以通过SecA和SecY追踪易位多肽链。在ATP水解的捕获过渡态中，SecA的双螺旋指靠近多肽，而SecA的钳通过诱导短β链以不依赖于序列的方式与多肽相互作用。考虑到以前的生物化学和生物物理数据，我们的结构是一致的模型，其中的双螺旋指和钳合作在ATP酶循环移动多肽通过通道。
The Sec61/SecY channel allows the translocation of many proteins across the eukaryotic endoplasmic reticulum membrane or the prokaryotic plasma membrane. In bacteria, most secretory proteins are transported post-translationally through the SecY channel by the SecA ATPase. How a polypeptide is moved through the SecA-SecY complex is poorly understood, as structural information is lacking. Here, we report an electron cryo-microscopy (cryo-EM) structure of a translocating SecA-SecY complex in a lipid environment. The translocating polypeptide chain can be traced through both SecA and SecY. In the captured transition state of ATP hydrolysis, SecA’s two-helix finger is close to the polypeptide, while SecA’s clamp interacts with the polypeptide in a sequence-independent manner by inducing a short β-strand. Taking into account previous biochemical and biophysical data, our structure is consistent with a model in which the two-helix finger and clamp cooperate during the ATPase cycle to move a polypeptide through the channel.