title: AFA-I, a cloned afimbrial X-type adhesin from a human pyelonephritic Escherichia coli strain. Purification and chemical, functional and serologic characterization.
abstract: AFA-I, a mannose-resistant, P-independent, X-binding afimbrial Escherichia coli adhesin was purified from a recombinant strain and chemically, functionally and serologically characterized. AFA-I exists on the bacterial surface and free as a macromolecular aggregate in the supernatant of spent culture medium. It is composed of a single, repeating 16-kDa polypeptide subunit. The AFA-I protein amino acid composition is remarkable for the presence of 22% non-polar hydrophobic residues and 2.5-3.0 cysteines per subunit. Since AFA-I travels as a monomer in sodium dodecyl sulfate/polyacrylamide gel electrophoresis under non-reducing conditions, no disulfide bonds exist between subunits and at least one free sulfhydryl per subunit is available. The AFA-I N-terminal amino acid sequence residues 1-24 was unrelated to E. coli fimbrial sequences; however, the N-terminus of AFA-I and GV-12, another E. coli afimbrial protein, was asparagine. HB101 (pIL 14), the AFA-I recombinant strain, agglutinated only human and gorilla erythrocytes, indicating a preference for receptor molecules on the red cells of man and the anthropoid apes. AFA-I did not bind glycophorin A or sialyl glycosides and is therefore distinct from the E. coli X-binding adhesins with M and S specificity. The AFA-I receptor was found to be abundant and diffusely distributed on HeLa tissue culture monolayer cell surfaces by indirect fluorescent microscopy. Anti-AFA-I sera bound AFA-I in Western blots of 4 out of 16 X-binding E. coli urine isolates. They did not bind MS or P pili. AFA-I may be exemplary of an adhesin class significant for the pathogenesis of human urinary tract infections.
authors.forename: W
authors.initials: W
authors.lastname: Walz
authors.forename: M A
authors.initials: MA
authors.lastname: Schmidt
authors.forename: A F
authors.initials: AF
authors.lastname: Labigne-Roussel
authors.forename: S
authors.initials: S
authors.lastname: Falkow
authors.forename: G
authors.initials: G
authors.lastname: Schoolnik
mesh_terms: D018830:Adhesins, Escherichia coli; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000942:Antigens, Bacterial / Q000302:isolation & purification*; D001426:Bacterial Proteins / Q000276:immunology / Q000302:isolation & purification*; D001665:Binding Sites; D003001:Cloning, Molecular; D003101:Collodion; D004926:Escherichia coli / Q000032:analysis* / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology; D006367:HeLa Cells; D006386:Hemagglutination Tests; D006801:Humans; D008856:Microscopy, Fluorescence; D011704:Pyelonephritis / Q000382:microbiology; D013045:Species Specificity
chemical_list: D018830:Adhesins, Escherichia coli; D000596:Amino Acids; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D003101:Collodion