title: Conformational studies on a unique bis-sulfated glycolipid using NMR spectroscopy and molecular dynamics simulations.
abstract: The time-averaged solution conformation of a unique bis-sulfated glycolipid (HSO3)2-2,6Manalpha-2Glcalpha-1-sn-2,3-O-alkylglycerol , was studied in terms of the torsional angles of two glycosidic linkages, phi (H1-C1-O-Cx) and psi (C1-O-Cx-Hx), derived from heteronuclear three-bond coupling constants (3JC,H), and inter-residual proton-proton distances from J-HMBC 2D and ROESY experiments, respectively. The dihedral angles of Glcalpha1Gro in glycolipids were determined for the first time. The C1-C4 diagonal line of the alpha-glucose ring makes an angle of approximately 120 degrees with the glycerol backbone, suggesting that the alpha-glucose ring is almost parallel to the membrane surface in contrast with the perpendicular orientation of the beta-isomer. Furthermore, minimum-energy states around the conformation were estimated by Monte Carlo/stochastic dynamics (MCSD) mixed-mode simulations and the energy minimization with assisted model building and energy refinement (AMBER) force field. The Glcalpha1Gro linkage has a single minimum-energy structure. On the other hand, three conformers were observed for the Manalpha2Glc linkage. The flexibility of Manalpha2Glc was further confirmed by the absence of inter-residual hydrogen bonds which were judged from the temperature coefficients of the chemical shifts, ddelta/dT (-10-3 p.p.m. degrees C-1), of hydroxy protons. The conformational flexibility may facilitate interaction of extracellular substances with both sulfate groups.
authors.affiliation: Department of Biochemistry, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Iida-Tanaka
authors.forename: K
authors.initials: K
authors.lastname: Fukase
authors.forename: H
authors.initials: H
authors.lastname: Utsumi
authors.forename: I
authors.initials: I
authors.lastname: Ishizuka
mesh_terms: D003198:Computer Simulation; D005947:Glucose / Q000737:chemistry; D006017:Glycolipids / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D009010:Monte Carlo Method; D011487:Protein Conformation; D013696:Temperature
chemical_list: D006017:Glycolipids; D005947:Glucose