title: Distinct glycan-charged phosphodolichol carriers are required for the assembly of the pentasaccharide N-linked to the Haloferax volcanii S-layer glycoprotein.
abstract: In Archaea, dolichol phosphates have been implicated as glycan carriers in the N-glycosylation pathway, much like their eukaryal counterparts. To clarify this relation, highly sensitive liquid chromatography/mass spectrometry was employed to detect and characterize glycan-charged phosphodolichols in the haloarchaeon Haloferax volcanii. It is reported that Hfx. volcanii contains a series of C(55) and C(60) dolichol phosphates presenting saturated isoprene subunits at the α and ω positions and sequentially modified with the first, second, third and methylated fourth sugar subunits comprising the first four subunits of the pentasaccharide N-linked to the S-layer glycoprotein, a reporter of N-glycosylation. Moreover, when this glycan-charged phosphodolichol pool was examined in cells deleted of agl genes encoding glycosyltransferases participating in N-glycosylation and previously assigned roles in adding pentasaccharide residues one to four, the composition of the lipid-linked glycans was perturbed in the identical manner as was S-layer glycoprotein N-glycosylation in these mutants. In contrast, the fifth sugar of the pentasaccharide, identified as mannose in this study, is added to a distinct dolichol phosphate carrier. This represents the first evidence that in Archaea, as in Eukarya, the oligosaccharides N-linked to glycoproteins are sequentially assembled from glycans originating from distinct phosphodolichol carriers.
authors.affiliation: Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Guan
authors.forename: Shai
authors.initials: S
authors.lastname: Naparstek
authors.forename: Lina
authors.initials: L
authors.lastname: Kaminski
authors.forename: Zvia
authors.initials: Z
authors.lastname: Konrad
authors.forename: Jerry
authors.initials: J
authors.lastname: Eichler
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004288:Dolichol Phosphates / Q000737:chemistry / Q000378:metabolism*; D006031:Glycosylation; D019622:Haloferax volcanii / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015394:Molecular Structure; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D004288:Dolichol Phosphates; D008562:Membrane Glycoproteins; D009844:Oligosaccharides; D011134:Polysaccharides; C055764:S-layer proteins