Interaction of prodigiosin with HSA and β-Lg:Spectroscopic and molecular docking studies

Human serum albumin (HSA) and bovine beta-lactoglobulin (beta-Lg) are both introduced as blood and oral carrier scaffolds with high affinity for a wide range of pharmaceutical compounds. Prodigiosin, a natural three pyrrolic compound produced by Serratia marcescens, exhibits many pharmaceutical properties associated with health benefits. In the present study, the interaction of prodigiosin with HSA and beta-Lg was investigated using fluorescence spectroscopy, circular dichroism (CD) and computational docking. Prodigiosin interacts with the Sudlow's site I of HSA and the calyx of beta-Lg with association constant of 4.41 x 10(4) and 1.99 x 10(4) M (1) to form 1 : 1 and 2 : 3 complexes at 300 K, respectively. The results indicated that binding of prodigiosin to HSA and beta-Lg caused strong fluorescence quenching of both proteins through static quenching mechanism. Electrostatic and hydrophobic interactions are the major forces in the stability of PG-HSA complex with enthalpy-and entropy-driving mode, although the formation of prodigiosin-beta-Lg complex is entropy-driven hydrophobic associations. CD spectra showed slight conformational changes in both proteins due to the binding of prodigiosin. Moreover, the ligand displacement assay, pH-dependent interaction and protein-ligand docking study confirmed that the prodigiosin binds to residues located in the subdomain IIA and IIIA of HSA and central calyx of beta-Lg. (C) 2016 Elsevier Ltd. All rights reserved.