RESUMO
Afa/Dr family of adhesins are produced by pathogenic Escherichia coli strains that are especially prevalent in chronic diarrhoeal and recurrent urinary tract infections. Most notably, they are found in up to 50% of cystitis cases in children and 30% of pyelonephritis in pregnant women. Afa/Dr adhesins are capped surface fibrils that mediate recognition of the host and subsequent bacterial internalization. Using the newly solved three-dimensional structure of the minimal invasive complex (AfaDE) combined with biochemical and cellular assays, we reveal the architecture of the fibrillar cap and identify a novel mode of synergistic integrin recognition.
Assuntos
Adesinas de Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Adesinas de Escherichia coli/química , Adesinas de Escherichia coli/genética , Sequência de Aminoácidos , Aderência Bacteriana/genética , Aderência Bacteriana/fisiologia , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Fímbrias Bacterianas/genética , Fímbrias Bacterianas/metabolismo , Espectroscopia de Ressonância Magnética , Microscopia de Fluorescência , Modelos Moleculares , Dados de Sequência Molecular , Ligação ProteicaRESUMO
Pathogenic bacteria possess adhesion protein complexes that play essential roles in targeting host cells and in propagating infection. Although each family of adhesion proteins is generally associated with a specific human disease, the Dr family from Escherichia coli is a notable exception, as its members are associated with both diarrheal and urinary tract infections. These proteins are reported to form both fimbrial and afimbrial structures at the bacterial cell surface and target a common host cell receptor, the decay-accelerating factor (DAF or CD55). Using the newly solved three-dimensional structure of AfaE, we have constructed a robust atomic resolution model that reveals the structural basis for assembly by donor strand complementation and for the architecture of capped surface fibers.
Assuntos
Adesinas de Escherichia coli/química , Escherichia coli/química , Estrutura Terciária de Proteína , Adesinas de Escherichia coli/genética , Adesinas de Escherichia coli/metabolismo , Sequência de Aminoácidos , Antígenos CD55/química , Antígenos CD55/metabolismo , Cristalografia por Raios X , Escherichia coli/metabolismo , Escherichia coli/patogenicidade , Fímbrias Bacterianas , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Ressonância Magnética Nuclear Biomolecular , Subunidades Proteicas/química , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , Alinhamento de Sequência , Ressonância de Plasmônio de SuperfícieRESUMO
Pathogenic Escherichia coli expressing Afa/Dr adhesins are able to cause both urinary tract and diarrheal infections. The Afa/Dr adhesins confer adherence to epithelial cells via interactions with the human complement regulating protein, decay accelerating factor (DAF or CD55). Two of the Afa/Dr adhesions, AfaE-III and DraE, differ from each other by only three residues but are reported to have several different properties. One such difference is disruption of the interaction between DraE and CD55 by chloramphenicol, whereas binding of AfaE-III to CD55 is unaffected. Here we present a crystal structure of a strand-swapped trimer of wild type DraE. We also present a crystal structure of this trimer in complex with chloramphenicol, as well as NMR data supporting the binding position of chloramphenicol within the crystal. The crystal structure reveals the precise atomic basis for the sensitivity of DraE-CD55 binding to chloramphenicol and demonstrates that in contrast to other chloramphenicol-protein complexes, drug binding is mediated via recognition of the chlorine "tail" rather than via intercalation of the benzene rings into a hydrophobic pocket.