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    • Keywords


      Concanavalin A; wheat germ agglutinin; fluorescence; difference absorption; temperature-jump; stopped-flow

    • Abstract


      The binding of fluorescently labelled carbohydrates to concanavalin A and wheat germ agglutinin was studied at equilibrium and by the stopped-flow and temperature jump relaxation methods. Ligand were mainly die 4-methylumbelliferyl glycosides of α (1 → 2)-linked manno-oligosaccharides and of β (1 → 4)-linked chito oligosaccharides as limited homologous series. They offer distinct advantages, parti cularly for kinetic studies.

      Enthalpie and kinetic considerations suggest that concanavalin A specifically binds a single mannopyranosyl group in α (1 →2)-linked manno-oligosaccharides. This occurs preferentially at the non-reducing end. Glycosylation of a carbohydrate withe.g. an aryl group does not afect die binding kinetics and for all carbohydrates the association rate is comparable but relatively slow, which indicates that a common process is involved in the binding of all carbohydrates to concanavalin A. The affinity of a carbohydrate for concanavalin A is determined by the dissociation-rate parameter, resulting in a longer residence time for a better ligand.

      Interaction of chito-oligosaccharides with wheat germ agglutinin is complex. With the larger members of the 4-methylumbelliferyl chito-oligosaccharides, binding studies were only possible at low fractional saturation to avoid formation of unsoluble complexes. The binding kinetics of wheat germ agglutinin are faster than with concanavalin A and are consistent with a wheat germ agglutinin binding region composed of two adjacent subsites. For binding of the monoside as well as the bioside, two consistent kinetic models apply. They have common that for each ligand there exist two complexes with comparable population.

    • Author Affiliations


      Frank G Loontiens1 Robert M Clegg2 Anita Van Landschoot3

      1. Laboratory for Biochemistry, State University of Ghent, Ledeganckstraat 35, Ghent - B-9000, Belgium
      2. Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Gottingen, Germany
      3. Laboratory for Microbiology, State University of Ghent, Ledeganckstraat 35, Ghent - B-9000, Belgium
    • Dates

  • Journal of Biosciences | News

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