While DNA encodes protein structure, glycans provide a complementary layer of information to protein function. As a prime example of the significance of glycans, the ability of the cell surface receptor CD44 to bind its ligand, hyaluronan, is modulated by N-glycosylation. However, the details of this modulation remain unclear. Based on atomistic simulations and NMR, we provide evidence that CD44 has multiple distinct binding sites for hyaluronan, and that N-glycosylation modulates their respective roles. We find that non-glycosylated CD44 favors the canonical sub-micromolar binding site, while glycosylated CD44 binds hyaluronan with an entirely different micromolar binding site. Our findings show (for the first time) how glycosylation can alter receptor affinity by shielding specific regions of the host protein, thereby promoting weaker binding modes. The mechanism revealed in this work emphasizes the importance of glycosylation in protein function and poses a challenge for protein structure determination where glycosylation is usually neglected.

• MeSH
• Hyaluronan Receptors genetics   ultrastructure   MeSH
• Cell Adhesion genetics   MeSH
• Glycosylation MeSH
• Protein Conformation * MeSH
• Hyaluronic Acid genetics   MeSH
• Humans MeSH
• Magnetic Resonance Spectroscopy MeSH
• Polysaccharides genetics   MeSH
• Receptors, Cell Surface genetics   MeSH
• Protein Binding genetics   MeSH
• Binding Sites genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Hyaluronan Receptors MeSH
• Hyaluronic Acid MeSH
• Polysaccharides MeSH
• Receptors, Cell Surface MeSH

High-resolution ultrasound spectroscopy and isothermal titration calorimetry were used to characterize interactions between hyaluronan and arginine oligomers. The molecular weight of arginine oligomer plays an important role in interactions with hyaluronan. Interactions were observable for arginine oligomers with eight monomer units and longer chains. The effect of the ionic strength and molecular weight of hyaluronan on interactions was tested. In an environment with increased ionic strength, the length of the arginine oligomer was crucial. Generally, sufficiently high ionic strength suppresses interactions between hyaluronan and arginine oligomers, which demonstrated interactions in water. From the point of view of the molecular weight of hyaluronan, the transition between the rod conformation and the random coil conformation appeared to be important.

• Keywords
• arginine, high-resolution ultrasound spectroscopy, hyaluronan, interaction, isothermal titration calorimetry,
• Publication type
• Journal Article MeSH