title: Glycosylation of the Escherichia coli TibA self-associating autotransporter influences the conformation and the functionality of the protein.
abstract: The self-associating autotransporters (SAATs) are multifunctional secreted proteins of Escherichia coli, comprising the AIDA-I, TibA and Ag43 proteins. One of their characteristics is that they can be glycosylated. Glycosylation of AIDA-I and Ag43 have been investigated, but not that of TibA. It is still not clear whether glycosylation of the SAATs affect their structure or their functionality. Therefore, we have looked at the effects of glycosylation on the TibA adhesin/invasin. TibA is glycosylated by TibC, a specific glycosyltransferase, and the two genes are encoded in an operon. In this study, we have found that the glycosylation of TibA is not limited to the extracellular functional domain, as previously observed with AIDA-I and Ag43. We have determined that unglycosylated TibA is not able to promote the adhesion of bacteria on cultured epithelial cell, even though it is still able to promote invasion, biofilm formation and autoaggregation of bacteria. We have purified the glycosylated and unglycosylated forms of TibA, and determined that TibA is less stable when not glycosylated. We finally observed that glycosylation affects the oligomerisation of TibA and that unglycosylated TibA is locked in a conformation that is not suited for adhesion. Our results suggest that the effect of glycosylation on the functionality of TibA is indirect.
authors.affiliation: Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Côté
authors.forename: Marie-Ève
authors.initials: MÈ
authors.lastname: Charbonneau
authors.forename: Michael
authors.initials: M
authors.lastname: Mourez
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006031:Glycosylation / Q000187:drug effects; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D018830:Adhesins, Escherichia coli; D010455:Peptides; C557497:TibA protein, E coli; D012965:Sodium Chloride; D010447:Peptide Hydrolases