Thermodynamic and Kinetic Parameters of Four Drugs Toward Beta‐2 Adrenergic Receptor Were Measured Robustly and Accurately Through a Chromatographic Column With CotB1 Peptide‐Mediated Immobilization

Thermodynamics and kinetics of drug–protein interactions are key indices for evaluating pharmacological activity during the early stages of drug discovery. In this work, the recombinant beta‐2 adrenergic receptor (β 2 AR) with the fusion of Halo tag or CotB1 peptide (CotB1p) tag was immobilized onto silica gels for preparing the two affinity chromatographic columns. Two experimental models, such as the injection amount‐dependent method and nonlinear chromatography, were employed to measure equilibrium constants and rate constants of four drugs, including bambuterol, salbutamol, clorprenaline, and tulobuterol, toward β 2 AR. Compared with nonlinear chromatography, the binding constants measured by the injection amount‐dependent method were more comparable to those from the radio binding assay. CotB1p‐mediated immobilization yielded larger association constants ( K A ) and the smaller dissociation rate constants ( k d ) of drug‐β 2 AR interaction, suggesting that the small‐sized CotB1p tag has less interference of protein conformations and the binding sites’ microenvironment than the large‐sized Halo tag. Thermodynamic analysis revealed that four drugs were spontaneously bound to β 2 AR, and the bindings between them were mainly driven by electrostatic interactions. Our results indicated that the CotB1p‐mediated immobilization strategy, resulting in the robust and accurate measurement of the binding parameters of ligand–receptor interaction, will bring new perspectives in applying affinity chromatography in the research fields of drug screening and drug–protein interaction.