A structural motif is the recognition site for a new family of bacterial protein O-glycosyltransferases.
The Escherichia coli Adhesin Involved in Diffuse Adherence (AIDA-I) is a multifunctional protein that belongs to the family of monomeric autotransporters. This adhesin can be glycosylated by the AIDA-associated heptosyltransferase (Aah). Glycosylation appears to be restricted to the extracellular domain of AIDA-I, which comprises imperfect repeats of a 19-amino-acid consensus sequence and is predicted to form a β-helix. Here, we show that Aah homologues can be found in many Gram-negative bacteria, including Citrobacter rodentium. We demonstrated that an AIDA-like protein is glycosylated in this species by the Aah homologue. We then investigated the substrate recognition mechanism of the E. coli Aah heptosyltransferase. We found that a peptide corresponding to one repeat of the 19-amino-acid consensus is sufficient for recognition and glycosylation by Aah. Mutagenesis studies suggested that, unexpectedly, Aah recognizes a structural motif typical of β-helices, but not a specific sequence. In agreement with this finding, we observed that the extracellular domain of the Bordetella pertussis pertactin, a β-helical polypeptide lacking the 19-amino-acid consensus sequence, could be glycosylated by Aah. Overall, our findings suggest that Aah represents the prototype of a new large family of bacterial protein O-glycosyltransferases that modify various substrates recognized through a structural motif.
Canada Research Chair on Bacterial Animal Diseases, Université de Montréal, Faculté de Médecine Vétérinaire St-Hyacinthe, 3200 Sicotte, St-Hyacinthe, Québec, Canada.
Marie-Ève
MÈ
Charbonneau
Jean-Philippe
JP
Côté
M Florencia
MF
Haurat
Bela
B
Reiz
Sébastien
S
Crépin
Frédéric
F
Berthiaume
Charles M
CM
Dozois
Mario F
MF
Feldman
Michael
M
Mourez
D018830:Adhesins, Escherichia coli / Q000737:chemistry*; D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry*; D001886:Bordetella pertussis / Q000201:enzymology; D044082:Citrobacter rodentium / Q000201:enzymology; D016384:Consensus Sequence; D004926:Escherichia coli / Q000201:enzymology*; D006031:Glycosylation; D016695:Glycosyltransferases / Q000737:chemistry*; D010802:Phylogeny; D016415:Sequence Alignment; D013379:Substrate Specificity
D018830:Adhesins, Escherichia coli; D001426:Bacterial Proteins; D016695:Glycosyltransferases; C086735:heptosyltransferase