Glycoproteomics of Haloferax volcanii reveals an extensive glycoproteome and concurrence of different N-glycosylation pathways

Glycosylation is one of the most complex post-translational protein modifications. Its importance has been established not only for eukaryotes but also for a variety of prokaryotic cellular processes, such as biofilm formation, motility and mating. However, comprehensive glycoproteomic analyses are largely missing in prokaryotes. Here we extend the phenotypic characterisation of N-glycosylation pathway mutants in Haloferax volcanii and provide a detailed glycoproteome for this model archaeon through the mass spectrometric analysis of intact glycopeptides. Using in-depth glycoproteomic datasets generated for the wild-type and mutant strains as well as a reanalysis of datasets within the Archaeal Proteome Project, we identify the largest archaeal glycoproteome described so far. We further show that different N-glycosylation pathways can modify the same glycosites under the same culture conditions. The extent and complexity of the Hfx. volcanii N-glycoproteome revealed here provides new insights into the roles of N-glycosylation in archaeal cell biology.