A structural motif is the recognition site for a new family of bacterial protein O-glycosyltransferases

作者：Charbonneau Marie Eve; Cote Jean Philippe; Haurat M Florencia; Reiz Bela; Crepin Sebastien; Berthiaume Frederic; Dozois Charles M; Feldman Mario F; Mourez Michael^*

来源：Molecular Microbiology, 2012, 83(5): 894-907.

DOI：10.1111/j.1365-2958.2012.07973.x

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 beta-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 beta-helices, but not a specific sequence. In agreement with this finding, we observed that the extracellular domain of the Bordetella pertussis pertactin, a beta-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.

• 出版日期2012-3