Fig 5.
The working model of the Hfx. volcanii N-glycosylation pathway. Select Asn residues of the Hfx. volcanii S-layer glycoprotein are modified by a pentasaccharide comprising a hexose, 2 hexuronic acids, a methyl ester of hexuronic acid and a terminal mannose residue. Based on the findings of the present study and earlier reports (16,17,23–25,33), a working model of the Hfx. volcanii N-glycosylation pathway is provided. AglJ, AglG, AglI, AglE and AglD are assigned roles in either modifying dolichol phosphates or adding sugars to dolichol phosphate-bound sugars. AglB serves as the oligosaccharyltransferase, while AglF, AglP and AglM serve various sugar processing roles. At present, the flippase(s) responsible for delivering the lipid-charged glycans across the plasma membrane remain to be defined and are indicated by question marks. dolP, dolichol phosphate; NDP, nucleoside diphosphate.