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 (K (SV) similar to 10(4) M (-1)) and moderate binding affinity (n similar to 0.5). The standard free energy change (a dagger GA degrees A similar to -25 kJ mol(-1)) indicates that binding is spontaneous. No significant change in a dagger GA degrees observed after unfolding of domain I or domain III. The standard change in enthalpy (a dagger HA degrees) and entropy (a dagger SA degrees) show that ionic and hydrophobic interactions are important in the binding. Computational studies revealed that the inter-domain helix h10(DOMI)-h1(DOMII) of BSA is the region of binding of curcumin, 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.