Esterase activity and conformational changes of bovine serum albumin toward interaction with mephedrone: Spectroscopic and computational studies

Abstract

The present work is a brief overview of the effect of psychostimulant drug mephedrone hydrochloride (4MMC) on a transport protein, bovine serum albumin (BSA). The binding effect of 4MMC on BSA has been investigated by using UV-visible, steady-state fluorescence, time-resolved fluorescence, fluorescence resonance energy transfer, Fourier transform infrared, circular dichroism, and molecular docking method. 4-Methylmephedrone quenched the intrinsic fluorescence of BSA by static quenching mechanism, which was further confirmed by time-resolved fluorescence. The absorption spectrum of BSA in the presence of various concentrations of 4MMC reveals the change in the absorption bands of BSA-4MMC complex. The binding constant between 4MMC and BSA was calculated to be of the order of 104 Lmol−1. The thermodynamic parameters such as molar enthalpy change (∆H), molar Gibbs free energy change (∆G), and molar entropy contribution (∆S) were obtained by the van't Hoff equation. The values obtained suggested that the binding mechanism was entropic driven and the major forces involved are hydrophobic in nature. The fluorescence resonance energy transfer result indicates the high probability of energy transfer from Trp residue of BSA to the 4MMC (r = 2.01 nm). Fourier transform infrared and CD results showed that 4MMC induced secondary structural changes in BSA. The esterase-like activity of BSA in presence of 4MMC further validated our CD results, confirming the distortion and change in functionality of protein upon binding with 4MMC. Molecular docking analysis showed that 4MMC principally bind at the II site (subdomain IIIA) of BSA.