Structural requirements for heparan sulphate self-association.

Area of Science:

• Biochemistry
• Glycobiology
• Molecular Biology

Background:

• Heparan sulphate (HS) is a complex glycosaminoglycan involved in numerous biological processes.
• Understanding HS self-association is key to elucidating its functional roles.
• Previous studies suggest HS chains can interact with each other, but the molecular basis remains unclear.

Purpose of the Study:

• To investigate the mechanisms underlying heparan sulphate self-association.
• To identify the specific chemical features of HS essential for chain-chain interactions.
• To explore the influence of molecular conformation on HS self-interaction.

Main Methods:

• Affinity chromatography using heparan sulphate-agarose matrices.
• Fractionation of beef-lung heparan sulphate.
• Chemical modifications of heparan sulphate chains (N-desulphation, N-acetylation, carboxyl reduction, periodate oxidation).
• Elution studies using radiolabeled HS and various competing glycosaminoglycans.

Main Results:

• Heparan sulphate chains exhibit self-affinity, binding preferentially to cognate HS on matrices.
• N-desulphation and N-acetylation abolished HS chain-chain interaction.
• Dermatan and chondroitin sulphates showed some affinity for HS-agarose.
• Modified HS chains (N-desulphated, carboxyl-reduced, periodate-oxidised) lost their ability to displace bound HS.
• Heparin's displacing ability was also abolished by periodate oxidation.

Conclusions:

• Heparan sulphate self-association is highly dependent on overall molecular conformation.
• N-sulphate and carboxylate groups are essential for maintaining HS secondary structure and self-interaction.
• The integrity of the D-glucuronate residue is critical for proper HS chain conformation and binding.