Structure determination of the glycolipid sulfate from the extreme halophile Halobacterium cutirubrum

A sulfur-containing glycolipid, accounting for ca. 25% of the total polar lipids, has been isolated from the extreme halophile Halobacterium cutirubrum. The ammonium salt of the lipid was found to have the molecular formula C(61)H(117)O(21)S.NH(4), and on strong acid hydrolysis it yielded 2,3-di-O-phytanyl-sn-glycerol, glucose, mannose, galactose, and sulfate in equimolar proportions. Infrared and NMR spectra indicated the presence of a secondary sulfate group. Solvolysis of the lipid in 0.004 m HCl in tetrahydrofuran resulted in rapid release of inorganic sulfate and formation of galactosyl-mannosyl-glucosyl diphytanyl glycerol ether. With higher acid concentration (0.25 m methanolic HCl), stepwise hydrolysis of monosaccharide units occurred, giving mannosyl-glucosyl glycerol diphytanyl ether and monoglucosyl glycerol diphytanyl ether. The position of attachment of the sugars and of the sulfate group was determined by methylation of the free acid form of the glycolipid sulfate, followed by acid hydrolysis and gas-liquid chromatographic analysis of the partially methylated sugars as the alditol acetates. The configuration of the glycosidic linkages was established both by optical rotation measurements and by specific enzymatic hydrolysis. The results obtained established the structure as 2,3-di-O-phytanyl-1-O-[beta-d-galactopyranosyl-3'-sulfate-(1' -->6')-O-alpha-d-mannopyranosyl-(1' --> 2')-O-alpha-d-glucopyranosyl]-sn-glycerol.