Dynamic Properties of Bacterial Adhesions

描述(由申请人提供)：该提案的主要目标是开发一幅关于机械力如何影响微生物粘连功能状态的全面结构图。特定的黏附蛋白使细菌能够识别导致各种活体宿主或环境利基的黏附和定植的配体，最终导致感染。越来越多的实验观察表明，体液剪切流动产生的机械力正在调节粘附素与其配体的亲和力和选择性。为了测试机械力改变粘附素结构和功能状态的程度，我们建议表征最常见的细菌粘附素-FimH-的动态性质，这是肠杆菌和弧菌1型(甘露糖敏感)菌毛的凝集素样粘附亚单位。在我们的初步研究过程中，我们已经确定了大肠杆菌FimH粘附素的不同结构变体，其中剪切流可以诱导它们与靶细胞的优先结合，显然是通过在单甘露糖苷和三甘露糖苷受体之间切换它们的特异性。为了建立结构假说，作用于结合位点的机械力如何影响FimH的三级结构，我们已经并将进行引导分子动力学模拟，在受体结合残基和FimH凝集素结构域的C末端之间施加张力。要全面了解粘附素在静态和动态条件下的结构-功能关系，需要结合X射线结晶学和新的强大的纳米分析工具来探测、表征和模拟与功能相关的非平衡蛋白质结构。

DESCRIPTION (provided by the applicant): The main goal of the proposal is to develop a comprehensive structural picture of how mechanical force affects the functional state of microbial adhesions. Specific adhesive proteins enable bacteria to recognize ligands leading to the adhesion and colonization of various living hosts or environmental niches, and finally infection. A growing number of experimental observations indicate that mechanical forces generated by shear-flow of body fluids are modulating the affinity and selectivity of adhesins to their ligands. In order to test the extent to which mechanical forces may alter the structure and thus the functional states of adhesins, we propose to characterize the dynamic properties of the most common type of bacterial adhesin - FimH -that is a lectin-like adhesive subunit of type 1 (mannose-sensitive) fimbria of Enterobacteria and Vibrio. In the course of our preliminary studies we have identified distinct structural variants of the Escherichia coli FimH adhesin where shear-flow can induce their preferential binding to target cells, obviously by switching their specificity between the mono-mannoside and tri-mannoside receptors. To develop structural hypotheses how mechanical forces acting on the binding site may affect the tertiary structure of FimH, we have been and will be conducting steered molecular dynamics simulations in which tension is applied between the receptor-binding residues and the C-terminal end of the FimH lectin domain. Deriving a comprehensive understanding of the structure-function relationship of adhesins under static and dynamic conditions requires that molecular biology tools are employed in concert with X-ray crystallography and novel powerful nano-analytical tools to probe, characterize and simulate non-equilibrium protein structures as they relate to function.