Cryo-EM structure of the bifunctional secretin complex of Thermus thermophilus
Cryo-EM structure of the bifunctional secretin complex of Thermus thermophilus
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DOI：
10.7554/elife.30483
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发表时间：
2017-12-27
期刊：
影响因子：
7.7
通讯作者：
Averhoff, Beate
中科院分区：
文献类型：
--
作者：
D'Imprima, Edoardo;Salzer, Ralf;Averhoff, Beate
分泌素形成跨革兰氏阴性菌外膜的多聚体通道，其介导底物的输入或输出和/或IV型皮利的挤出。嗜热栖热菌的分泌素复合物是757个残基的PiIQ蛋白的低聚物，对于DNA摄取和菌毛挤出是必需的。在这里，我们提出的cryo-EM结构的双功能复杂的分辨率类似于7埃使用一种新的重建协议。13个原聚体形成一个大的周质结构域的6个堆叠环和一个分泌素结构域的外膜。将PiIQ蛋白的同源性模型拟合到cryo-EM图中。发现覆盖促胰液素的外膜外的冠状结构不是PiIQ的一部分。分泌素结构域的突变破坏了冠，废除DNA摄取，表明冠在自然转化中的核心作用。
Secretins form multimeric channels across the outer membrane of Gram-negative bacteria that mediate the import or export of substrates and/or extrusion of type IV pili. The secretin complex of Thermus thermophilus is an oligomer of the 757-residue PiIQ protein, essential for DNA uptake and pilus extrusion. Here, we present the cryo-EM structure of this bifunctional complex at a resolution of similar to 7 angstrom using a new reconstruction protocol. Thirteen protomers form a large periplasmic domain of six stacked rings and a secretin domain in the outer membrane. A homology model of the PiIQ protein was fitted into the cryo-EM map. A crown-like structure outside the outer membrane capping the secretin was found not to be part of PiIQ. Mutations in the secretin domain disrupted the crown and abolished DNA uptake, suggesting a central role of the crown in natural transformation.