The carbohydrate-binding specificity and molecular modelling of Canavalia maritima and Dioclea grandiflora lectins

RESUMO

The carbohydrate-binding specificity of lectins from the seeds of Canavalia maritima and Dioclea grandiflora was studied by hapten-inhibition of haemagglutination using various sugars and sugar derivatives as inhibitors, including N-acetylneuraminic acid and N-acetylneuraminic acid and N-acetylmuramic acid. Despite some discrepancies, both lectins exhibited a very similiar carbohydrate-binding specificity as previously reported for other lectins from Diocleinae (tribe Phaseoleae, sub-tribe Diocleinae). Accordingly, both lectins exhibited almost identical hydropathic profiles and their three-dimensional models built up from the atomic coordinates of ConsA looked very similar. However, doking experiments of glucose and mannose in their monosaccharide-binding sites, by comparison with the ConA-mannose complex used as a model, reveled conformational changes in side chains of the animo acid residues invlved in the binding of monosaccharides. These results fully agree with crystallographic data showing that binding of specific ligands to ConsA requires conformational chances of this monosaccharide-binding site.