Deciphering the biomolecular interaction of β-resorcylic acid with human lysozyme: A biophysical and bioinformatics outlook

Abstract

The binding mechanism between human lysozyme (Lyz) and β-resorcylic acid (BR) was systematically examined by various biophysical and computational techniques. The studies like ultraviolet absorbance and steady-state fluorescence confirmed the complex formation with binding constant in the order of 103 M−1. The mechanism of fluorescence quenching of Lyz was found to be static. The average binding distance between Lyz and BR was calculated by FRET as per Forster’s theory. The changes in conformation and microenvironment in the secondary structure of Lyz in the presence of BR were confirmed by techniques like synchronous, three-dimensional fluorescence spectroscopy, Red edge excitation shift (REES) and circular dichroism (CD). The different temperature-based fluorescence experiments highlighted that the reaction is spontaneous and exothermic in nature. The van der Waals and hydrogen bonding are the main contributing forces in the complex formation as is evident from the negative values of enthalpy (ΔH) and entropy (ΔS). Further, the results obtained from in vitro experiments were also reaffirmed by in silico molecular docking, predicting the active binding site of BR in Lyz. HOMO-LUMO energy gap in BR was estimated by density functional theory (DFT) studies. Moreover, the effects of β-cyclodextrin, metal ions, and vitamins on the binding of BR with Lyz were also studied.