title: An extended spectrum of target proteins and modification sites in the general O-linked protein glycosylation system in Neisseria gonorrhoeae.
abstract: The bacterial human pathogen  Neisseria gonorrhoeae expresses a general O-linked protein glycosylation (Pgl) system known to target at least 12 membrane-associated proteins. To facilitate a better understanding of the mechanisms, significance and function of this glycosylation system, we sought to further delineate the target proteome of the Pgl system. To this end, we employed immunoaffinity enrichment of glycoproteins using a monoclonal antibody against the glycan moiety. Enzymatically generated peptides were subsequently analyzed by MS to identify glycopeptides and glycosylation sites. In this way, we increase the total number of known glycoproteins in N. gonorrhoeae to 19. These new glycoproteins are involved in a wide variety of extracytoplasmic functions. By employing collision fragmentation, we mapped nine new glycosylation sites, all of which were serine. No target sequon was readily apparent, although attachment sites were most often localized with regions of low sequence complexity. Moreover, we found that 5 of the proteins were modified with more than one glycan. This work thus confirms and extends earlier observations on the structural features of Neisseria glycoproteins.
authors.affiliation: Department of Molecular Biosciences, Center for Molecular Biology and Neuroscience, and Glyconor Mass Spectrometry and Proteomics Unit, University of Oslo, 0316 Oslo, Norway.
authors.forename: Jan Haug
authors.initials: JH
authors.lastname: Anonsen
authors.forename: Åshild
authors.initials: Å
authors.lastname: Vik
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Egge-Jacobsen
authors.forename: Michael
authors.initials: M
authors.lastname: Koomey
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000032:analysis* / Q000737:chemistry; D001665:Binding Sites; D019295:Computational Biology / Q000379:methods; D030541:Databases, Genetic; D006020:Glycopeptides / Q000032:analysis* / Q000737:chemistry; D006031:Glycosylation; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009344:Neisseria gonorrhoeae / Q000737:chemistry*; D011134:Polysaccharides / Q000032:analysis / Q000737:chemistry; D020543:Proteome / Q000032:analysis* / Q000737:chemistry; D040901:Proteomics / Q000379:methods; D012694:Serine / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D006020:Glycopeptides; D011134:Polysaccharides; D020543:Proteome; D012694:Serine