Disulfide bridge formation between SecY and a translocating polypeptide localizes the translocation pore to the center of SecY.
Disulfide bridge formation between SecY and a translocating polypeptide localizes the translocation pore to the center of SecY.
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DOI：
10.1083/jcb.200412019
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发表时间：
2005-04-25
期刊：
影响因子：
--
通讯作者：
Rapoport TA
中科院分区：
文献类型：
--
作者：
Cannon KS;Or E;Clemons WM Jr;Shibata Y;Rapoport TA
在其生物合成过程中，许多蛋白质通过由异源三聚体Sec61/SecY复合物形成的亲水通道穿过膜。这个通道是在Sec61/SecY的多个拷贝的界面处形成，还是如最近解析的詹氏甲烷球菌SecY复合物的X射线结构所表明的那样是单体复合物所固有的，这是一个有争议的问题。通过在大肠杆菌SecY的不同位置引入单个半胱氨酸，并检测其与转运链中的单个半胱氨酸形成二硫键的能力，我们提供了证据表明转运多肽穿过SecY复合物的中心。在沙漏形孔中会形成收缩部位的残基处观察到最强的交联。这表明该通道与转运多肽仅有限接触，从而使转运所需的能量最小化。
During their biosynthesis, many proteins pass through the membrane via a hydrophilic channel formed by the heterotrimeric Sec61/SecY complex. Whether this channel forms at the interface of multiple copies of Sec61/SecY or is intrinsic to a monomeric complex, as suggested by the recently solved X-ray structure of the Methanococcus jannaschii SecY complex, is a matter of contention. By introducing a single cysteine at various positions in Escherichia coli SecY and testing its ability to form a disulfide bond with a single cysteine in a translocating chain, we provide evidence that translocating polypeptides pass through the center of the SecY complex. The strongest cross-links were observed with residues that would form a constriction in an hourglass-shaped pore. This suggests that the channel makes only limited contact with a translocating polypeptide, thus minimizing the energy required for translocation.
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