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Glycosylation with heptose residues mediated by the aah gene product is essential for adherence of the AIDA‐I adhesin
Author(s) -
Benz Inga,
Schmidt M. Alexander
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02487.x
Subject(s) - bacterial adhesin , open reading frame , biology , heptose , glycosylation , mutant , gene product , biochemistry , haemophilus ducreyi , gene , tunicamycin , escherichia coli , plasmid , peptide sequence , gene expression , haemophilus influenzae , pasteurellaceae , unfolded protein response , antibiotics
The diffuse adherence of Escherichia coli strain 2787 (O126:H27) is mediated by the autotransporter adhesin AIDA‐I ( a dhesin‐ i nvolved‐in‐ d iffuse‐ a dherence) 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 ≈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 ’ ( a utotransporter‐ a dhesin‐ h eptosyltransferase). Glycosylation by heptoses represents a novel protein modification in eubacteria .