Inter-domain helix h10 DOMI -h1 DOMII is important in the molecular interaction of bovine serum albumin with curcumin: spectroscopic and computational analysis

The importance of domain II in the molecular interaction of bovine serum albumin (BSA) with curcumin was investigated by fluorescence spectroscopy and molecular docking. At pH 7.4 BSA is in its native state. Domain III of BSA unfolds at pH 4.0, and domains I and III unfold in the presence of 5 M urea. Curcumin has a high quenching constant (KSV * 10 4 M -1 ) and moderate binding affinity (n * 0.5). The standard free energy change (DG� * -25 kJ mol -1 ) indicates that binding is spontaneous. No significant change in DGobserved after unfolding of domain I or domain III. The standard change in enthalpy (DH� ) and entropy (DS� ) show that ionic and hydrophobic interactions are important in the binding. Computational studies revealed that the inter-domain helix h10DOMI-h1DOMII of BSA is the region of binding of cur- cumin, and residues Arg198 and Arg208 are important in binding. The binding site is located between sub-domains IB and IIA, and overlaps drug binding site-1.