title: The F4 fimbrial chaperone FaeE is stable as a monomer that does not require self-capping of its pilin-interactive surfaces.
abstract: Many Gram-negative bacteria use the chaperone-usher pathway to express adhesive surface structures, such as fimbriae, in order to mediate attachment to host cells. Periplasmic chaperones are required to shuttle fimbrial subunits or pilins through the periplasmic space in an assembly-competent form. The chaperones cap the hydrophobic surface of the pilins through a donor-strand complementation mechanism. FaeE is the periplasmic chaperone required for the assembly of the F4 fimbriae of enterotoxigenic Escherichia coli. The FaeE crystal structure shows a dimer formed by interaction between the pilin-binding interfaces of the two monomers. Dimerization and tetramerization have been observed previously in crystal structures of fimbrial chaperones and have been suggested to serve as a self-capping mechanism that protects the pilin-interactive surfaces in solution in the absence of the pilins. However, thermodynamic and biochemical data show that FaeE occurs as a stable monomer in solution. Other lines of evidence indicate that self-capping of the pilin-interactive interfaces is not a mechanism that is conservedly applied by all periplasmic chaperones, but is rather a case-specific solution to cap aggregation-prone surfaces.
authors.affiliation: Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, Belgium. ivmolle@vub.ac.be
authors.forename: Inge
authors.initials: I
authors.lastname: Van Molle
authors.forename: Kristof
authors.initials: K
authors.lastname: Moonens
authors.forename: Lieven
authors.initials: L
authors.lastname: Buts
authors.forename: Abel
authors.initials: A
authors.lastname: Garcia-Pino
authors.forename: Santosh
authors.initials: S
authors.lastname: Panjikar
authors.forename: Lode
authors.initials: L
authors.lastname: Wyns
authors.forename: Henri
authors.initials: H
authors.lastname: De Greve
authors.forename: Julie
authors.initials: J
authors.lastname: Bouckaert
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003432:Cross-Linking Reagents / Q000494:pharmacology; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D036781:Fimbriae Proteins / Q000378:metabolism; D005976:Glutaral / Q000494:pharmacology; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D009391:Nephelometry and Turbidimetry; D011487:Protein Conformation; D011489:Protein Denaturation; D025941:Protein Interaction Mapping; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D018830:Adhesins, Escherichia coli; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; C494388:FaeG protein, E coli; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; C070012:faeE protein, E coli; D036781:Fimbriae Proteins; D005976:Glutaral