title: Mechanism of the Association Pathways for a Pair of Fast and Slow Binding Ligands of HIV-1 Protease.
abstract: Equilibrium constants, together with kinetic rate constants of binding, are key factors in the efficacy and safety of drug compounds, informing drug design. However, the association pathways of protein-ligand binding, which contribute to their kinetic behaviors, are little understood. In this work, we used unbiased all-atom molecular dynamics (MD) simulations with an explicit solvent model to study the association processes of protein-ligand binding. Using the HIV protease (HIVp)-xk263 and HIVp-ritonavir protein-ligand systems as cases, we observed that ligand association is a multistep process involving diffusion, localization, and conformational rearrangements of the protein, ligand, and water molecules. Moreover, these two ligands preferred different routes of binding, which reflect two well-known binding mechanisms: induced-fit and conformation selection models. Our study shows that xk263 has a stronger capacity for desolvating surrounding water molecules, thereby inducing a semiopen conformation of the HIVp flaps (induced-fit model). In contrast, the slow dehydration characteristic of ritonavir allows for gradual association with the binding pocket of HIVp when the protein's flap conformation is fully open (conformation selection model). By studying the mechanism of ligand association and understanding the role of solvent molecules during the binding event, we can obtain a different perspective on the mechanism of macromolecule recognition, providing insights into drug discovery.
authors.affiliation: Department of Chemistry, University of California, Riverside , Riverside, California 92521, United States.
authors.forename: Yu-Ming M
authors.identifier: 0000-0003-3257-6170
authors.initials: YM
authors.lastname: Huang
authors.affiliation: Department of Chemistry, University of California, Riverside , Riverside, California 92521, United States.
authors.forename: Mark Anthony V
authors.initials: MA
authors.lastname: Raymundo
authors.affiliation: Department of Chemistry, University of California, Riverside , Riverside, California 92521, United States.|ChemConsulting LLC , Frederick, Maryland 21704, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Chemistry, University of California, Riverside , Riverside, California 92521, United States.
authors.forename: Chia-En A
authors.initials: CA
authors.lastname: Chang
mesh_terms: D016333:HIV Protease / Q000737:chemistry* / Q000378:metabolism*; D015497:HIV-1 / Q000201:enzymology*; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D011487:Protein Conformation; D019438:Ritonavir / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D016333:HIV Protease; D019438:Ritonavir