Specific residues in the N-terminal domain of FimH stimulate type 1 fimbriae assembly in Escherichia coli following the initial binding of the adhesin to FimD usher.
Type 1 fimbriae are assembled by the chaperone-usher pathway where periplasmic protein complexes formed between fimbrial subunits and the FimC chaperone are recruited by the outer membrane protein FimD (the usher) for their ordered polymerization and export. FimH adhesin initiates and stimulates type 1 fimbriae polymerization by interacting with FimD. Previously we showed that the N-terminal lectin domain of FimH (N-FimH) is necessary for binding of the adhesin to FimD. In this work, we have selected mutants in N-FimH that reduce the levels of adhesin and type 1 fimbriae displayed in Escherichia coli without altering the levels of FimH in the periplasm. The selected mutations are mostly concentrated in residues G15, N46 and D47. In contrast to other mutations isolated that simply affect binding of FimH to FimD (e.g. C3Y), these variants associate to FimD and alter its susceptibility to trypsin digestion similarly to wild-type FimH. Importantly, their mutant phenotype is rescued when FimD is activated in vivo by the coexpression of wild-type FimH. Altogether, these data indicate that residues G15, N46 and D47 play an important role following initial binding of FimH to FimD for efficient type 1 fimbriae polymerization by this outer membrane usher.
Munera
Diana
D
Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, 28049 Madrid, Spain.
Palomino
Carmen
C
Fernández
Luis Angel
LA
D018830:Adhesins, Escherichia coli / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D017354:Point Mutation; D017434:Protein Structure, Tertiary / Q000235:genetics; D014357:Trypsin / Q000737:chemistry
D018830:Adhesins, Escherichia coli; D000596:Amino Acids; D029968:Escherichia coli Proteins; C489283:fimD protein, E coli; C058769:fimH protein, E coli; D036781:Fimbriae Proteins; D014357:Trypsin