Isolation and characterization of dolichol-linked oligosaccharides from Haloferax volcanii

Biosynthesis of procaryotic glycoproteins has been studied in some detail only in the extreme halophile Halobacterium halobium. To extend these studies for a moderate halophile, dolichol phosphate-linked oligosaccharides were isolated and characterized from Haloferax volcanii. Mannosyl (beta 1-->4)galactosyl phosphodolichol could be characterized as a main component by GC/MS permethylation analysis, mass spectrometry and 1H-NMR-spectroscopy. Furthermore, two additional components, present in lower quantities, were partially characterized and identified as a tetrasaccharyl phosphodolichol containing mannose, galactose, and rhamnose in the ratio of 2:1:1 as well as another dihexosyl phosphodolichol. Both the latter compounds contain an additional charged group. All these oligosaccharides were found to be linked to a dolichol consisting of 11 or 12 isoprene units including a saturated omega-terminal isoprene residue.