Glycosylation with heptose residues mediated by the aah gene product is essential for adherence of the AIDA-I adhesin

Mol Microbiol. 2001 Jun;40(6):1403-13. doi: 10.1046/j.1365-2958.2001.02487.x.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adhesins, Escherichia coli / genetics
  • Adhesins, Escherichia coli / immunology
  • Adhesins, Escherichia coli / metabolism*
  • Amino Acid Sequence
  • Bacterial Adhesion / physiology
  • Carbohydrates / analysis
  • Escherichia coli / physiology
  • Escherichia coli Proteins*
  • Gene Order
  • Glycosylation
  • Glycosyltransferases / genetics*
  • Glycosyltransferases / metabolism
  • HeLa Cells / microbiology
  • Heptoses / metabolism*
  • Humans
  • Molecular Sequence Data
  • Open Reading Frames
  • Plasmids
  • Protein Processing, Post-Translational
  • Sequence Homology, Amino Acid


  • AIDA-I protein, E coli
  • Adhesins, Escherichia coli
  • Carbohydrates
  • Escherichia coli Proteins
  • Heptoses
  • Glycosyltransferases
  • autotransporter-adhesin-heptosyltransferase, E coli