Molecular interaction and esterase activity of bovine serum albumin with Pazopanib using multi-spectroscopic techniques and molecular docking

Abstract

This work delves into the binding dynamics of a promising anti-cancer drug Pazopanib (PZB) with bovine serum albumin (BSA), a mammalian plasma protein carrier with incredible ligand-binding properties. PZB is a tyrosine kinase inhibitor (TKI) used as a monotherapy against advanced renal cell carcinoma, soft tissue sarcoma, and liver fibrosis. Drug-albumin interactions vary with concentration, affecting drug efficacy and toxicity. Herein, we have investigated the binding mechanism of PZB with BSA at higher drug concentrations (5 × 10⁻⁶ mol/kg - 4 × 10⁻⁵ mol/kg) than albumin (3 × 10⁻⁶ mol/kg) using techniques like absorption, steady-state fluorescence, FRET, FT-IR, synchronous fluorescence, CD, and molecular docking. The intrinsic BSA fluorescence quenches with gradual increase in concentration of PZB via static quenching. The binding constant was found to be moderate (6.497 × 10⁴ mol ⁻¹.kg) and it has only one binding site. The Förster distance (r) indicated probable transfer of energy between the donor BSA and acceptor PZB. The major interacting forces are hydrophobic forces and hydrogen bonding. Conformational change in the protein framework was revealed from synchronous fluorescence, FT-IR, and CD studies. Competitive binding experiments as well as docking studies suggest that PZB binds to site I (subdomain IIA) of BSA. The increase in kinetic parameters reveals that the catalytic efficiency of BSA is enhanced on PZB interaction.