Unusual N-terminal ααβαββα Fold of PilQ from Thermus thermophilus Mediates Ring Formation and Is Essential for Piliation
Unusual N-terminal ααβαββα Fold of PilQ from Thermus thermophilus Mediates Ring Formation and Is Essential for Piliation
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DOI：
10.1074/jbc.m111.334912
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发表时间：
2012-03-09
影响因子：
4.8
通讯作者：
Averhoff, Beate
中科院分区：
文献类型：
--
作者：
Burkhardt, Janin;Vonck, Janet;Averhoff, Beate
天然转化系统中的DNA易位子是一种复杂的系统，对游离DNA的摄取至关重要，并为适应不断变化的环境条件提供了强有力的机制。在自然转化机制中，外膜分泌素被认为形成多聚体孔以吸收外部DNA。最近，我们报道了一种新的结构的DNA转运分泌素复合物，PilQ，在嗜热栖热菌HB 27包括一个稳定的锥杯结构和六个环结构与一个大的中央通道。在这里，我们报告的结构和功能分析的一组N-末端PilQ删除衍生物在T。嗜热菌HB 27。我们确定了136个N-末端残基，表现出不寻常的α α β α β α折叠作为一个环建设域。删除这个域有一个戏剧性的影响抽搐的运动，粘附，和pilization，但没有废除自然转化。这些结果为T.嗜热菌不是自然转化所必需的。截短的复合物不受影响，内外膜协会，表明136个N-末端残基是不必要的膜靶向。对截短的PilQ单体的复合物形成的分析显示，残基136的下游区域是多聚化所需的，残基207的下游区域是单体稳定性所必需的。可能的影响，我们的研究结果的DNA摄取的机制进行了讨论。
DNA translocators of natural transformation systems are complex systems critical for the uptake of free DNA and provide a powerful mechanism for adaptation to changing environmental conditions. In natural transformation machineries, outer membrane secretins are suggested to form a multimeric pore for the uptake of external DNA. Recently, we reported on a novel structure of the DNA translocator secretin complex, PilQ, in Thermus thermophilus HB27 comprising a stable cone and cup structure and six ring structures with a large central channel. Here, we report on structural and functional analyses of a set of N-terminal PilQ deletion derivatives in T. thermophilus HB27. We identified 136 N-terminal residues exhibiting an unusual alpha alpha beta alpha beta beta alpha fold as a ring-building domain. Deletion of this domain had a dramatic effect on twitching motility, adhesion, and piliation but did not abolish natural transformation. These findings provide clear evidence that the pilus structures of T. thermophilus are not essential for natural transformation. The truncated complex was not affected in inner and outer membrane association, indicating that the 136 N-terminal residues are not essential for membrane targeting. Analyses of complex formation of the truncated PilQ monomers revealed that the region downstream of residue 136 is required for multimerization, and the region downstream of residue 207 is essential for monomer stability. Possible implications of our findings for the mechanism of DNA uptake are discussed.