In N-glycosylation in both Eukarya and Archaea, N-linked oligosaccharides are assembled on dolichol phosphate prior to transfer of the glycan to the protein target. However, whereas only the α-position isoprene subunit is saturated in eukaryal dolichol phosphate, both the α- and ω-position isoprene subunits are reduced in the archaeal lipid. The agents responsible for dolichol phosphate saturation remain largely unknown. The present study sought to identify dolichol phosphate reductases in the halophilic archaeon, Haloferax volcanii. Homology-based searches recognize HVO-1799 as a geranylgeranyl reductase. Mass spectrometry revealed that cells deleted of HVO-1799 fail to fully reduce the isoprene chains of H. volcanii membrane phospholipids and glycolipids. Likewise, the absence of HVO-1799 led to a loss of saturation of the ω-position isoprene subunit of C55 and C60 dolichol phosphate, with the effect of HVO-1799 deletion being more pronounced with C60 dolichol phosphate than with C55 dolichol phosphate. Glycosylation of dolichol phosphate in the deletion strain occurred preferentially on that version of the lipid saturated at both the α- and ω-position isoprene subunits.
|Number of pages||11|
|Journal||Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids|
|State||Published - 1 Jun 2012|
- Dolichol phosphate
- Geranylgeranyl reductase
- Haloferax volcanii