Analysis of Astaxanthin Binding to Transmembrane Transporter Protein Cluster Determinant 36 Using Molecular Docking and Surface Plasmon Resonance

Purpose: To investigate the binding interaction of astaxanthin with the transmembrane transporter protein cluster determinant 36 (CD36). Methods: Molecular docking was used to simulate the binding interaction between astaxanthin and CD36, the interaction parameters were obtained using an algorithm, the number of binding sites was determined, and the best matching model was established. Moreover, surface plasmon resonance (SPR) was used to measure the binding and dissociation constants of intermolecular interactions. Results: Astaxanthin entered the hydrophobic cavity inside CD36, and the docking binding energy was −11.70 kcal/mol, suggesting a dose-dependent effect. Besides, the equilibrium dissociation constant K_D was 1.00 × 10^-6 mol/L, indicating that astaxanthin bound to CD36 with high affinity, and the kinetic curves showed that the binding mode of astaxanthin and CD36 was slow binding and slow dissociation. Astaxanthin bound to more amino acids of CD36 through hydrophobic interaction. Unlike lutein and β-carotene, which formed weak van der Waals force with the polar amino acid Asn53 of CD36, astaxanthin formed hydrogen bonding with Asn53, which may be partly responsible for the high-affinity binding between astaxanthin and CD36. Furthermore, it was inferred that the ketone group on the terminal ring of astaxanthin or α-hydroxy ketone formed by hydroxyl and ketone groups played a certain role in the formation of hydrogen bonds. Conclusion: Astaxanthin interacts spontaneously with CD36 with high affinity, and the binding mode is slow binding and slow dissociation, contributing to efficient transmembrane transport.