title: Interdomain interaction in the FimH adhesin of Escherichia coli regulates the affinity to mannose.
abstract: FimH is a mannose-specific adhesin located on the tip of type 1 fimbriae of Escherichia coli that is capable of mediating shear-enhanced bacterial adhesion. FimH consists of a fimbria-associated pilin domain and a mannose-binding lectin domain, with the binding pocket positioned opposite the interdomain interface. By using the yeast two-hybrid system, purified lectin and pilin domains, and docking simulations, we show here that the FimH domains interact with one another. The affinity for mannose is greatly enhanced (up to 300-fold) in FimH variants in which the interdomain interaction is disrupted by structural mutations in either the pilin or lectin domains. Also, affinity to mannose is dramatically enhanced in isolated lectin domains or in FimH complexed with the chaperone molecule that is wedged between the domains. Furthermore, FimH with native structure mediates weak binding at low shear stress but shifts to strong binding at high shear, whereas FimH with disrupted interdomain contacts (or the isolated lectin domain) mediates strong binding to mannose-coated surfaces even under low shear. We propose that interactions between lectin and pilin domains decrease the affinity of the mannose-binding pocket via an allosteric mechanism. We further suggest that mechanical force at high shear stress separates the two domains, allowing the lectin domain to switch from a low affinity to a high affinity state. This shift provides a mechanism for FimH-mediated shear-enhanced adhesion by enabling the adhesin to form catch bond-like interactions that are longer lived at high tensile force.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington 98105, USA.
authors.forename: Pavel
authors.initials: P
authors.lastname: Aprikian
authors.forename: Veronika
authors.initials: V
authors.lastname: Tchesnokova
authors.forename: Brian
authors.initials: B
authors.lastname: Kidd
authors.forename: Olga
authors.initials: O
authors.lastname: Yakovenko
authors.forename: Vladimir
authors.initials: V
authors.lastname: Yarov-Yarovoy
authors.forename: Elena
authors.initials: E
authors.lastname: Trinchina
authors.forename: Viola
authors.initials: V
authors.lastname: Vogel
authors.forename: Wendy
authors.initials: W
authors.lastname: Thomas
authors.forename: Evgeni
authors.initials: E
authors.lastname: Sokurenko
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry* / Q000378:metabolism; D002448:Cell Adhesion; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000378:metabolism; D014644:Genetic Variation; D037102:Lectins / Q000737:chemistry; D008358:Mannose / Q000737:chemistry*; D008968:Molecular Conformation; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D018830:Adhesins, Escherichia coli; D037102:Lectins; C058769:fimH protein, E coli; D036781:Fimbriae Proteins; D008358:Mannose