O-Linked Glycosylation Ensures the Normal Conformation of the Autotransporter Adhesin Involved in Diffuse Adherence
Open Access
- 15 December 2007
- journal article
- research article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 189 (24), 8880-8889
- https://doi.org/10.1128/jb.00969-07
Abstract
The Escherichia coli adhesin involved in diffuse adherence (AIDA-I) is one of the few glycosylated proteins found in Escherichia coli . Glycosylation is mediated by a specific heptosyltransferase encoded by the aah gene, but little is known about the role of this modification and the mechanism involved. In this study, we identified several peptides of AIDA-I modified by the addition of heptoses by use of mass spectrometry and N-terminal sequencing of proteolytic fragments of AIDA-I. One threonine and 15 serine residues were identified as bearing heptoses, thus demonstrating for the first time that AIDA-I is O-glycosylated. We observed that unglycosylated AIDA-I is expressed in smaller amounts than its glycosylated counterpart and shows extensive signs of degradation upon heat extraction. We also observed that unglycosylated AIDA-I is more sensitive to proteases and induces important extracytoplasmic stress. Lastly, as was previously shown, we noted that glycosylation is required for AIDA-I to mediate adhesion to cultured epithelial cells, but purified mature AIDA-I fused to GST was found to bind in vitro to cells whether or not it was glycosylated. Taken together, our results suggest that glycosylation is required to ensure a normal conformation of AIDA-I and may be only indirectly necessary for its cell-binding function.Keywords
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