Intermolecular interaction of coreopsin with β-lactoglobulin at varied pH values: Experiment, dynamics simulation and IGM analysis.

In this investigation, underlying intermolecular interaction of coreopsin and β-Lactoglobulin (β-Lg) under various pH values were explored using multiexperiments, dynamics simulation and independent gradient model (IGM). Fluorescence analysis indicated that coreopsin interacted with β-Lg mainly through hydrogen bonds and van der Waals forces, which were validated by IGM, and molecular mechanics poisson boltzmann surface area (mm-PBSA) results. Based on multispectral and zeta potential-particle size analyses, the binding of coreopsin to β-Lg induced significant alterations in the conformation, crystallinity, charge distribution and particle size. Molecular simulations revealed obvious differences in the binding sites of coreopsin toward monomer, dimer and tetramer, thereby resulting in diverse dynamics behaviors. The mm-PBSA analysis indicated that residues PRO38, GLN59 and LYS138 contributed greatly to electrostatic energy during the binding of coreopsin with monomer, dimer, and tetramer, respectively. Several amino acid residues maintained the stability of complexes by providing van der Waals energy.