X-ray structure of a protein-conducting channel
X-ray structure of a protein-conducting channel
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DOI：
10.1038/nature02218
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发表时间：
2004-01-01
期刊：
影响因子：
64.8
通讯作者：
Rapoport, TA
中科院分区：
文献类型：
--
作者：
van den Berg, B;Clemons, WM;Rapoport, TA
一种保守的异源三聚体膜蛋白复合物，Sec61或SecY复合物，形成一个蛋白质传导通道，使多肽能够穿过膜或整合到膜中。我们报道了詹氏甲烷球菌该复合物分辨率为3.2埃的晶体结构。该结构表明，异源三聚体的一个拷贝作为一个功能性的转运通道。α亚基有两个相连的部分，跨膜区段1 - 5和6 - 10，由γ亚基夹在一起。一个通向通道的细胞质漏斗被一个短螺旋堵塞。堵塞物的移位可将通道打开成一个“沙漏”形状，在其狭窄处有一圈疏水残基。这个环可能在转运的多肽周围形成一个密封，阻碍其他分子的渗透。该结构还表明了信号序列识别的机制以及新生膜蛋白的跨膜区段侧向进入脂质的机制，并指出了为转运提供驱动力的伙伴的结合位点。
A conserved heterotrimeric membrane protein complex, the Sec61 or SecY complex, forms a protein-conducting channel, allowing polypeptides to be transferred across or integrated into membranes. We report the crystal structure of the complex from Methanococcus jannaschii at a resolution of 3.2 Angstrom. The structure suggests that one copy of the heterotrimer serves as a functional translocation channel. The alpha-subunit has two linked halves, transmembrane segments 1-5 and 6-10, clamped together by the gamma-subunit. A cytoplasmic funnel leading into the channel is plugged by a short helix. Plug displacement can open the channel into an 'hourglass' with a ring of hydrophobic residues at its constriction. This ring may form a seal around the translocating polypeptide, hindering the permeation of other molecules. The structure also suggests mechanisms for signal-sequence recognition and for the lateral exit of transmembrane segments of nascent membrane proteins into lipid, and indicates binding sites for partners that provide the driving force for translocation.