Valency conversion in the type 1 fimbrial adhesin of Escherichia coli

FimH protein is a lectin-like adhesive subunit of type 1, or mannose-sensitive, fimbriae that are found on the surface of most Escherichia coli strains. All naturally occurring FimH variants demonstrate a conserved mannotriose-specific (i.e. multivalent) binding. Here, we demonstrate that replacement of residues 185-279 within the FimH pilin domain with a corresponding segment of the type 1C fimbrial adhesin FocH leads to a loss of the multivalent mannotriose-specific binding property accompanied by the acquisition of a distinct monomannose-specific (i.e. monovalent) binding capability. Bacteria expressing the monovalent hybrid adhesins were capable of binding strongly to uroepithelial tissue culture cells and guinea pig erythrocytes. They could not, however, agglutinate yeast or bind human buccal cells - functions readily accomplished by the E. coli-expressing mannotriose-specific FimH variants. Based on the relative potency of inhibiting compounds of different structures, the receptor binding site within monovalent FimH-FocH adhesin has an extended structure with an overall configuration similar to that within the multivalent FimH of natural origin. The monomannose-only specific phenotype could also be invoked by a single point mutation, E89K, located within the lectin domain of FimH, but distant from the receptor binding site. The structural alterations influence the receptor-binding valency of the FimH adhesin via distal effects on the combining pocket, obviously by affecting the FimH quaternary structure.

Sokurenko E.V. 1 , Schembri M.A.2 , Trintchina E. 1, 5 , Kjærgaard K.2 , Hasty D.L.3, 4 , Klemm P.2
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  • 1 Department of Microbiology, University of Washington, Seattle, WA 98195-7242, United States
  • 2 Section of Molecular Microbiology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark
  • 3 Department of Anatomy and Neurobiology, University of Tennessee, Memphis, TN 38163, United States
  • 4 VA Medical Centre, Memphis, TN 38104, United States
  • 5 Department of Microbiology, People's Friendship University, Moscow, Russian Federation
Ключевые слова
adhesin; article; electron microscopy; Escherichia coli; fimbria; nonhuman; point mutation; priority journal; protein conformation; protein domain; protein quaternary structure; structure activity relation; Adhesins, Bacterial; Adhesins, Escherichia coli; Agglutination; Amino Acid Sequence; Animals; Bacterial Adhesion; Cattle; Cells, Cultured; Cricetinae; Erythrocytes; Escherichia coli; Fimbriae Proteins; Lectins, C-Type; Mannose-Binding Lectins; Methylmannosides; Molecular Sequence Data; Phenotype; Point Mutation; Protein Binding; Protein Conformation; Receptors, Cell Surface; Recombinant Fusion Proteins; Ribonucleases; Sequence Homology, Amino Acid; Serum Albumin
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