Full-length, Oligomeric Structure of Wzz Determined by Cryoelectron Microscopy Reveals Insights into Membrane-Bound States
Full-length, Oligomeric Structure of Wzz Determined by Cryoelectron Microscopy Reveals Insights into Membrane-Bound States
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DOI：
10.1016/j.str.2017.03.017
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发表时间：
2017-05-02
期刊：
影响因子：
5.7
通讯作者：
Ford, Robert C.
中科院分区：
文献类型：
--
作者：
Collins, Richard F.;Kargas, Vasileios;Ford, Robert C.
Wzz是一种整合的内膜蛋白，参与调节脂多糖O-抗原聚糖的长度，并且对于许多革兰氏阴性病原体的毒力是必需的。在所有Wzz同源物中，大的周质结构域被提议通过两个跨膜螺旋锚定，但是没有关于跨膜和胞质结构域的信息。在这里，我们研究了纯化的低聚物Wzz复合物，使用冷冻电子显微镜和解决的跨膜区域内的半连续洗涤剂胶束。每个单体的跨膜螺旋显示右手超螺旋扭曲，并且不与相邻的跨膜结构域相互作用。建模，灵活的拟合和多尺度模拟方法被用来研究全长复杂的，并提供解释的影响，其寡聚状态的脂双层。基于结构和在硅片上的观察，我们提出了一种新的机制，O-抗原链长调节，调用协同作用的Wzz和它的聚合酶的合作伙伴，Wzy。
Wzz is an integral inner membrane protein involved in regulating the length of lipopolysaccharide O-antigen glycans and essential for the virulence of many Gram-negative pathogens. In all Wzz homologs, the large periplasmic domain is proposed to be anchored by two transmembrane helices, but no information is available for the transmembrane and cytosolic domains. Here we have studied purified oligomeric Wzz complexes using cryoelectron microscopy and resolved the transmembrane regions within a semi-continuous detergent micelle. The transmembrane helices of each monomer display a right-handed super-helical twist, and do not interact with the neighboring transmembrane domains. Modeling, flexible fitting and multiscale simulation approaches were used to study the full-length complex and to provide explanations for the influence of the lipid bilayer on its oligomeric status. Based on structural and in silico observations, we propose a new mechanism for O-antigen chain-length regulation that invokes synergy of Wzz and its polymerase partner, Wzy.