INFLUENCE OF THE EXTENT OF BRANCHING ON SOLUTION CONFORMATIONS OF COMPLEX OLIGOSACCHARIDES - A MOLECULAR-DYNAMICS AND NMR-STUDY OF A PENTA-ANTENNARY BISECTED N-GLYCAN

The solution conformation of an agalactosyl penta-antennary ''bisected '' N-linked glycan from hen ovomucoid has been determined using a comb ination of H-1-NMR NOE measurements and restrained molecular dynamics (MD) simulations, The majority of glycosidic linkages exhibited restri cted torsional fluctuations about the global minimum energy configurat ion, of an extent which was generally less than that observed in N-lin ked glycans with a smaller number of antennae. The locations of termin al galactose residues in the native glycan, which exhibit branch speci ficity, could not readily be rationalized in terms of relative accessi bility by the relevant galactosyltransferase of the various nonreducin g terminal 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) residues in th e agalactosyl glycan, suggesting either that the parent protein exhibi ts substantial control over glycosylation or that more than one transf erase is responsible for galactosylation.