NMR and molecular modeling studies on two glycopeptides from the carbohydrate-protein linkage region of connective tissue proteoglycans

Academic Article

Abstract

  • Complete 1H and 13C NMR assignments are reported for two glycopeptides representing the carbohydrate-protein linkage region of connective tissue proteoglycans. These glycopeptides are the octasaccharide hexapeptide, Ser(Glc(p)Aβ(1→3) Gal(p)β(1→3)Gal(p)β(1→4)Xyl(p)β)-Gly-Ser-Gly-Ser (Glc(p)Aβ(1→ 3)Gal(p)β(1→3)Gal(p)β(1→4)Xyl(p)β)-Gly (1), and the tetrasaccharide dipeptide, Ser(Glc(p)Aβ(1→3)Gal(p)β(1→3)Gal(p)β(1→ 4)Xyl(p)β)-Gly (2). The vicinal coupling constant data show that the monosaccharide residues adopt 4C1 chair conformations. Distance geometry/simulated annealing calculations using 2D NOESY derived distance constraints yielded a single family of structures for the tetrasaccharide moiety, with well defined interglycosidic linkage conformations. The (φ torsion angles of the glycosidic C1'-O1 bonds showed a strict preference for the -sc range whereas the Ψ torsion angles (O1-Cn) exhibited dependence upon the interglycosidic linkage position (-ac for β(1→3) linkage, +ac for β(1→4) linkage). The predominant conformation about the glycopeptide bond is φ = -sc and ψ = +ac. The presence of strong d(αN) (i, i + 1) NOE contacts, and the general absence of d(NN) (i, i + 1) contacts (except for a weak Ser-5/Gly-6 d(NN) contact) and the d(βN) (i, i + 1) contacts (except for Ser-1/Gly-2) in the ROESY spectrum, suggest that the backbone for 1 is predominantly in an extended conformation. A comparison of the ROESY data for 1 with those obtained from the unglycosylated hexapeptide (3) of the same sequence suggests that glycosylation has only a marginal influence on the backbone conformation of the hexapeptide.
  • Authors

    Published In

  • Glycobiology  Journal
  • Digital Object Identifier (doi)

    Author List

  • Agrawal PK; Jacquinet JC; Krishna NR
  • Start Page

  • 669
  • End Page

  • 677
  • Volume

  • 9
  • Issue

  • 7