Nilsson Lina M, Thomas Wendy E, Trintchina Elena, Vogel Viola, Sokurenko Evgeni V
Departments of Bioengineering and Microbiology, University of Washington, Seattle, WA 98195, USA.
J Biol Chem. 2006 Jun 16;281(24):16656-63. doi: 10.1074/jbc.M511496200. Epub 2006 Apr 19.
The FimH protein is the adhesive subunit of Escherichia coli type 1 fimbriae. It mediates shear-dependent bacterial binding to monomannose (1M)-coated surfaces manifested by the existence of a shear threshold for binding, below which bacteria do not adhere. The 1M-specific shear-dependent binding of FimH is consistent with so-called catch bond interactions, whose lifetime is increased by tensile force. We show here that the oligosaccharide-specific interaction of FimH with another of its ligands, trimannose (3M), lacks a shear threshold for binding, since the number of bacteria binding under static conditions is higher than under any flow. However, similar to 1M, the binding strength of surface-interacting bacteria is enhanced by shear. Bacteria transition from rolling into firm stationary surface adhesion as the shear increases. The shear-enhanced bacterial binding on 3M is mediated by catch bond properties of the 1M-binding subsite within the extended oligosaccharide-binding pocket of FimH, since structural mutations in the putative force-responsive region and in the binding site affect 1M- and 3M-specific binding in an identical manner. A shear-dependent conversion of the adhesion mode is also exhibited by P-fimbriated E. coli adhering to digalactose surfaces.
FimH蛋白是大肠杆菌1型菌毛的粘附亚基。它介导细菌与单甘露糖（1M）包被表面的剪切依赖性结合，这种结合表现为存在一个结合的剪切阈值，低于该阈值细菌就不会粘附。FimH对1M的特异性剪切依赖性结合与所谓的捕捉键相互作用一致，其寿命会因拉力而增加。我们在此表明，FimH与其另一种配体三甘露糖（3M）的寡糖特异性相互作用缺乏结合的剪切阈值，因为在静态条件下结合的细菌数量高于任何流动条件下的数量。然而，与1M类似，剪切会增强表面相互作用细菌的结合强度。随着剪切力增加，细菌从滚动转变为牢固地粘附在固定表面上。FimH延伸的寡糖结合口袋内1M结合亚位点的捕捉键特性介导了细菌在3M上的剪切增强结合，因为假定的力响应区域和结合位点的结构突变以相同方式影响1M和3M特异性结合。粘附在二半乳糖表面的P菌毛大肠杆菌也表现出粘附模式的剪切依赖性转变。
