A comprehensive calorimetric, spectroscopic, and molecular docking investigation to probe the interaction of colchicine with HEWL

Colchicine (Col), a naturally occurring alkaloid, has been used as an anti-inflammatory, anti-fibrotic, and anti-tumor drug. The present study reports in vitro interaction between Col and hen egg white lysozyme (HEWL) by spectroscopy, isothermal titration calorimetry (ITC), and molecular docking techniques. The fluorescence results indicated that Col quenches the intrinsic fluorescence of HEWL through static quenching mechanism which is also substantiated by UV-visible spectroscopy. The average distance (r) between donor (HEWL) and acceptor (Col) was evaluated by Forster's resonance energy transfer theory. Thermodynamic parameters obtained from ITC suggested that hydrophobic interaction plays a major role in the complex formation, and it is an entropically driven process. Col altered the secondary structure of HEWL revealed by circular dichroism which is further corroborated by synchronous, 3D fluorescence and FTIR techniques. In addition, molecular docking was employed to find out binding site of Col on HEWL and amino acid residues involved in the binding process. This study is expected to provide insights into the type of interaction and binding mechanism of Col with HEWL.