Assessment on malvidin-3-glucoside interaction with TLR4 via multi-spectroscopic analysis and molecular docking

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Toll-like receptor 4 (TLR4) is an innate immune receptor involved in glucolipid metabolism.
• Blueberries contain anthocyanins, notably malvidin-3-glucoside (Mv-3-glc), known for anti-inflammatory, hypoglycemic, and hypolipidemic effects.
• The mechanism by which Mv-3-glc exerts its effects, potentially through TLR4 binding, requires elucidation.

Purpose of the Study:

• To investigate the noncovalent interactions between malvidin-3-glucoside (Mv-3-glc) and Toll-like receptor 4 (TLR4).
• To determine the binding affinity and thermodynamic parameters of the Mv-3-glc-TLR4 complex.
• To identify the specific binding site and amino acid residues involved in the interaction.

Main Methods:

• Fluorescence spectroscopy to assess TLR4 intrinsic fluorescence quenching by Mv-3-glc.
• UV-Vis absorption spectroscopy to monitor complex formation.
• Molecular docking simulations to predict binding site and interactions.

Main Results:

• Mv-3-glc effectively quenched TLR4 intrinsic fluorescence, indicating binding.
• A stable, exothermic complex formed between Mv-3-glc and TLR4, with binding dependent on concentration, temperature, and pH.
• Thermodynamic analysis revealed hydrogen bonding and van der Waals forces as primary driving forces, consistent with molecular docking predictions.
• Molecular docking identified specific amino acid residues (Phe126, Ser127, Leu54, Ile153, Tyr131) in TLR4/MD-2 as the binding site for Mv-3-glc.

Conclusions:

• Malvidin-3-glucoside directly binds to Toll-like receptor 4.
• The interaction is characterized by hydrogen bonding and van der Waals forces.
• These findings support the therapeutic potential of blueberry anthocyanins in modulating glucolipid metabolism via TLR4.