NMR and modeling studies of protein-carbohydrate interactions:: Synthesis, three-dimensional structure, and recognition properties of a minimum hevein domain with binding affinity for chitooligosaccharides

HEV32, a 32-residue, truncated hevein locking eleven C-terminal amino acids, was synthesized by solid-phase methodology and correctly folded with three cysteine bridge pairs. The affinities of HEV32 for small chitin fragments-in the forms of N,N',N"-triacetylchitotriose ((GlcNAc)(3)) (millimolar) and N,N',N",N"',N"",N""'-hexaacetylchitohexaose ((GlcNAc)(6)) (micromolar)-as measured by NMR and fluorescence methods, are comparable with those of native hevein. The HEV32 ligand-binding process is enthalpy driven, while entropy opposes binding. The NMR structure of ligand-bound HEV32 in aqueous solution was determined to be highly similar to the NMR structure of ligand-bound hevein.