State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, China.
PLoS One. 2013 Jul 26;8(7):e70144. doi: 10.1371/journal.pone.0070144. Print 2013.
The bacterial type IV pilus (T4P) is the strongest biological motor known to date as its retraction can generate forces well over 100 pN. Myxococcus xanthus, a δ-proteobacterium, provides a good model for T4P investigations because its social (S) gliding motility is powered by T4P. In this study, the interactions among M. xanthus T4P proteins were investigated using genetics and the yeast two-hybrid (Y2H) system. Our genetic analysis suggests that there is an integrated T4P structure that crosses the inner membrane (IM), periplasm and the outer membrane (OM). Moreover, this structure exists in the absence of the pilus filament. A systematic Y2H survey provided evidence for direct interactions among IM and OM proteins exposed to the periplasm. For example, the IM lipoprotein PilP interacted with its cognate OM protein PilQ. In addition, interactions among T4P proteins from the thermophile Thermus thermophilus were investigated by Y2H. The results indicated similar protein-protein interactions in the T4P system of this non-proteobacterium despite significant sequence divergence between T4P proteins in T. thermophilus and M. xanthus. The observations here support the model of an integrated T4P structure in the absence of a pilus in diverse bacterial species.
细菌 IV 型菌毛（T4P）是目前已知的最强生物马达，其缩回时可产生超过 100 pN 的力。粘细菌是δ-变形菌，是研究 T4P 的良好模型，因为其社会（S）滑动运动是由 T4P 提供动力的。在这项研究中，使用遗传学和酵母双杂交（Y2H）系统研究了 M. xanthus T4P 蛋白之间的相互作用。我们的遗传分析表明，存在一种整合的 T4P 结构，它穿过内膜（IM）、周质和外膜（OM）。此外，这种结构在没有菌毛丝的情况下存在。系统的 Y2H 调查提供了证据，证明暴露在周质中的 IM 和 OM 蛋白之间存在直接相互作用。例如，IM 脂蛋白 PilP 与它的同源 OM 蛋白 PilQ 相互作用。此外，还通过 Y2H 研究了嗜热菌 Thermus thermophilus 的 T4P 蛋白之间的相互作用。结果表明，尽管 T. thermophilus 和 M. xanthus 的 T4P 蛋白之间存在显著的序列差异，但在这个非保护菌的 T4P 系统中存在类似的蛋白-蛋白相互作用。这些观察结果支持了在不同细菌物种中存在整合的 T4P 结构而不存在菌毛的模型。
