title: Glycosylation with heptose residues mediated by the aah gene product is essential for adherence of the AIDA-I adhesin.
abstract: The diffuse adherence of Escherichia coli strain 2787 (O126:H27) is mediated by the autotransporter adhesin AIDA-I (adhesin-involved-in-diffuse-adherence) encoded by the plasmid-borne aidA gene. AIDA-I exhibits an aberrant mobility in denaturing gel electrophoresis. Deletion of the open reading frame (ORF) A immediately upstream of aidA restores the predicted mobility of AIDA-I, but the adhesin is no longer functional. This indicates that the mature AIDA-I adhesin is post-translationally modified and the modification is essential for adherence function. Labelling with digoxigenin hydrazide shows AIDA-I to be glycosylated. Using carbohydrate composition analysis, AIDA-I contains exclusively heptose residues (ratio heptose:AIDA-I approximately 19:1). The deduced amino acid sequence of the cytoplasmic open reading frame (ORF) A gene product shows homologies to heptosyltransferases. In addition, the modification was completely abolished in an ADP-glycero-manno-heptopyranose mutant. Our results provide direct evidence for glycosylation of the AIDA-I adhesin by heptoses with the ORF A gene product as a specific (mono)heptosyltransferase generating the functional mature AIDA-I adhesin. Consequently, the ORF A gene has been denoted 'aah' (autotransporter-adhesin-heptosyltransferase). Glycosylation by heptoses represents a novel protein modification in eubacteria.
authors.affiliation: Institut für Infektiologie - Zentrum für Molekularbiologie der Entzündung (ZMBE), Universitätsklinikum Münster, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Benz
authors.forename: M A
authors.initials: MA
authors.lastname: Schmidt
mesh_terms: D018830:Adhesins, Escherichia coli / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000502:physiology; D002241:Carbohydrates / Q000032:analysis; D004926:Escherichia coli / Q000502:physiology; D029968:Escherichia coli Proteins; D023061:Gene Order; D006031:Glycosylation; D016695:Glycosyltransferases / Q000235:genetics* / Q000378:metabolism; D006367:HeLa Cells / Q000382:microbiology; D006539:Heptoses / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010957:Plasmids; D011499:Protein Processing, Post-Translational; D017386:Sequence Homology, Amino Acid
chemical_list: C075559:AIDA-I protein, E coli; D018830:Adhesins, Escherichia coli; D002241:Carbohydrates; D029968:Escherichia coli Proteins; D006539:Heptoses; D016695:Glycosyltransferases; C433803:autotransporter-adhesin-heptosyltransferase, E coli