Structure of the Neisseria meningitidis outer membrane PilQ secretin complex at 12 Å resolution
Structure of the Neisseria meningitidis outer membrane PilQ secretin complex at 12 Å resolution
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DOI：
10.1074/jbc.m405971200
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发表时间：
2004-09-17
影响因子：
4.8
通讯作者：
Derrick, JP
中科院分区：
文献类型：
--
作者：
Collins, RF;Frye, SA;Derrick, JP
细菌病原体脑膜炎奈瑟菌从其细胞表面表达长而薄的可伸缩纤维（称为IV型毛），并在宿主定植和入侵期间利用这些粘附结构介导对上皮细胞的初级附着。PilQ是一种外膜蛋白复合物，对于这些毛在外膜上的易位至关重要。在这里，我们展示了用低温电子显微镜以12埃分辨率确定的PilQ复合物的结构。该结构的主要特征是一个大的中心空腔，由四个臂状特征组成，这些臂状特征从方形环状基础向上螺旋并相遇形成一个突出的帽区。腔体，贯穿中心的复杂，是连续的，有效地密封在顶部和底部。利用自取向分析和二维晶体检测表明，配合物具有较强的C4旋转对称性，而C12旋转对称性弱得多，这与PilQ具有真正的C4对称和C12准对称相一致。因此，我们认为该复合物是一种同十二聚体，由12个PilQ多肽链结合成三聚体的四聚体。PilQ复合体的结构，其大而明确的中心腔室，表明它可能不仅仅是外膜的被动入口，而且可能积极参与介导菌毛的组装或修饰。
The bacterial pathogen Neisseria meningitidis expresses long, thin, retractile fibers ( called type IV pili) from its cell surface and uses these adhesive structures to mediate primary attachment to epithelial cells during host colonization and invasion. PilQ is an outer membrane protein complex that is essential for the translocation of these pili across the outer membrane. Here, we present the structure of the PilQ complex determined by cryoelectron microscopy to 12 Angstrom resolution. The dominant feature of the structure is a large central cavity, formed by four arm features that spiral upwards from a squared ring base and meet to form a prominent cap region. The cavity, running through the center of the complex, is continuous and is effectively sealed at both the top and bottom. Analysis of the complex using self-orientation and by examination of two-dimensional crystals indicates a strong C4 rotational symmetry, with a much weaker C12 rotational symmetry, consistent with PilQ possessing true C4 symmetry with C12 quasisymmetry. We therefore suggest that the complex is a homododecamer, formed by association of 12 PilQ polypeptide chains into a tetramer of trimers. The structure of the PilQ complex, with its large and well defined central chamber, suggests that it may not function solely as a passive portal in the outer membrane, but could be actively involved in mediating pilus assembly or modification.