Mechanical Regulation of Ultra-Sensitivity in E. Coli Flagellar Motors

项目摘要 许多可移动的细菌物种所表现出的成群的运动性与这种快速入侵有关。 在尿路感染(UTIs)期间宿主的数量。每年，仅在美国，尿路感染就导致数千人死亡 这对公共医疗系统来说是一个巨大的负担。蜂群运动是与底物相关的 是由细菌鞭毛马达驱动的，这些马达旋转细胞外的螺旋细丝，产生对细胞的推力- 尸体。虽然趋化性不是蜂群所必需的，但分子开关的功能使 电机旋转方向的反转是必不可少的。该开关是由细胞内的Chey-P激活的 反应--受趋化网络调控的调节因子。基于Chey-P绑定，协作 多亚基开关内部的相互作用-复合体驱动逆时针(CCW)的协同转变 顺时针(CW)构象的可能性增加，导致旋转方向的变化。我们的 最近的结果表明，鞭毛马达感觉到与固体基质接触产生的机械力， 这就导致了开关的抑制。在很短的时间内，马达就能适应这些力并恢复 逆转方向的能力。然而，导致适应的分子基础仍然不清楚。 因此，迫切需要确定开关如何适应机械刺激以促进蜂群。 在没有这样的知识的情况下，利用抗病毒策略作为治疗方法的潜力 对抗蜂群介导的宿主入侵和抗生素耐药性可能仍将是有限的。我们的长期目标 是为了促进针对细菌的新的临床有用的抗病毒策略的开发 蜂拥而至和殖民。我们在这一应用中的总体目标是确定分子机制 因此，开关能够完美地适应机械信号并促进蜂群运动。我们的中心假设是 马达-机械感应(机械信号的感应)通过 开关内部变构和协同作用的调节。拟议工作的基本原理是 确定机械控制超敏感的机制可能会提供一个概念性的 制定干预开关适应和缓解蜂拥而至的战略的框架。在… 随着拟议研究的完成，我们期望能够定量地解释其机理。 潜在的开关--机械力对超敏感性的适应和调制。预计结果将 具有重要的积极影响，因为详细了解衬底附近的切换将提供 为生物医学设备中的新型衬底设计奠定了坚实的基础，包括导管，这将针对 电机开关，以抑制蜂拥而至。

PROJECT ABSTRACT Swarming motility, exhibited by many motile species of bacteria, has been implicated in the rapid invasion of hosts during urinary tract infections (UTIs). Annually, UTIs result in several thousand deaths in the US alone and represent a significant load on the public healthcare system. Swarming motility is substrate-associated and is driven by bacterial flagellar motors that rotate extracellular, helical filaments to generate thrust on the cell- body. Although chemotaxis is not required for swarming, the functioning of a molecular switch that enables reversals in the direction of motor-rotation is indispensable. The switch is activated by CheY-P, an intracellular response-regulator that is regulated by the chemotaxis network. Upon CheY-P-binding, cooperative interactions within the multi-subunit switch-complex drive concerted transitions from counterclockwise (CCW) to clockwise (CW) conformations with increasing likelihood, resulting in changes in the direction of rotation. Our recent results indicate that flagellar motors sense mechanical forces, arising from contact with solid substrates, and that leads to the inhibition of switching. In a short time the motor adapts to these forces and recovers the ability to reverse directions. However, the molecular underpinnings responsible for adaptation remain unclear. Thus, there is a critical need to determine how the switch adapts to mechanical stimuli to promote swarming. Without such knowledge, the potential to capitalize on antivirulence strategies as therapeutic approaches to combat swarming-mediated host-invasion and antibiotic resistance will likely remain limited. Our long-term goal is to contribute toward the development of new clinically useful antivirulence strategies that target bacterial swarming and colonization. Our overall objective in this application is to determine the molecular mechanisms whereby the switch adapts perfectly to mechanical signals and promotes swarming. Our central hypothesis is that motor-mechanosensing (sensing of mechanical signals) results in the tuning of ultra-sensitivity through the modulation of allosteric and cooperative interactions within the switch. The rationale for the proposed work is that a determination of the mechanism of mechanical control of ultra-sensitivity is likely to provide a conceptual framework for the development of strategies to interfere with switch adaptation, and to mitigate swarming. At the completion of the proposed research, it is our expectation to have quantitatively explained the mechanisms underlying switch-adaptation and modulation of ultra-sensitivity by mechanical forces. Results are expected to have an important positive impact because a detailed understanding of switching near substrates will provide a strong foundation for novel substrate-design in biomedical devices, including catheters, which will target the motor-switch to inhibit swarming.