Deciphering the structural attributes of protein-heparan sulfate interactions using chemo-enzymatic approaches and NMR spectroscopy.

Heparan sulfates (HS) is a polysaccharide found at the cell surface, where it mediates interactions with hundreds of proteins and regulates major pathophysiological processes. HS is highly heterogeneous and structurally complex and examples that define their structure-activity relationships remain limited. Here, in order to characterize a protein-HS interface and define the corresponding saccharide-binding domain, we present a chemo-enzymatic approach that generates 13C-labeled HS-based oligosaccharide structures. Nuclear magnetic resonance (NMR) spectroscopy, which efficiently discriminates between important or redundant chemical groups in the oligosaccharides, is employed to characterize these molecules alone and in interaction with proteins. Using chemokines as model system, docking based on NMR data on both proteins and oligosaccharides enable the identification of the structural determinant involved in the complex. This study shows that both the position of the sulfo groups along the chain and their mode of presentation, rather than their overall number, are key determinant and further points out the usefulness of these 13C-labeled oligosaccharides in obtaining detailed structural information on HS-protein complexes.