Preserving the membrane barrier for small molecules during bacterial protein translocation.
Preserving the membrane barrier for small molecules during bacterial protein translocation.
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DOI：
10.1038/nature10014
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发表时间：
2011-05-12
期刊：
影响因子：
64.8
通讯作者：
Rapoport, Tom A.
中科院分区：
文献类型：
--
作者：
Park, Eunyong;Rapoport, Tom A.
在细菌和古菌中，许多蛋白质通过SecY通道进行转运，在真核生物中则通过相关的Sec61通道。该通道呈沙漏形状，在膜的大约中间位置有一个狭窄的收缩部位，由氨基酸形成的孔环构成。通道的细胞质腔是空的，而细胞外腔则填充着一个短螺旋，即塞子，在蛋白质转运过程中它会移开。该通道运输大多肽但又阻止小分子（如离子或代谢物）通过的机制一直存在争议。在此，我们通过检测小分子通过野生型和突变型SecY通道的渗透情况，在完整的大肠杆菌细胞中研究了这一问题，这些通道要么处于静息状态，要么含有一条确定的正在转运的多肽链。在静息状态下，通道由孔环和塞子结构域密封。在转运过程中，孔环在多肽链周围形成类似垫圈的密封，防止小分子渗透。该通道在所有生物中的结构保守性表明，在蛋白质转运过程中维持膜屏障存在一种通用机制。
Many proteins are translocated through the SecY channel in bacteria and archaea, and the related Sec61 channel in eukaryotes. The channel has an hourglass shape with a narrow constriction approximately halfway across the membrane, formed by a pore ring of amino acids. While the cytoplasmic cavity of the channel is empty, the extra-cellular cavity is filled with a short helix, the plug, which moves out of the way during protein translocation. The mechanism by which the channel transports large polypeptides and yet prevents the passage of small molecules, such as ions or metabolites, has been controversial. Here, we have addressed this issuein intact E. coli cells by testing the permeation of small molecules through wild-type and mutant SecY channels, which are either in the resting state or contain a defined translocating polypeptide chain. In the resting state, the channel is sealed by both the pore ring and the plug domain. During translocation the pore ring forms a gasket-like seal around the polypeptide chain, preventing the permeation of small molecules. The structural conservation of the channel in all organisms suggests a universal mechanism by which the membrane barrier is maintained during protein translocation.
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