Structural and energetic effects of A2A adenosine receptor mutations on agonist and antagonist binding.

To predict structural and energetic effects of point mutationson ligand binding is of considerable interest in biochemistry and pharmacology. This is not only useful in connection with site-directed mutagenesisexperiments, but could also allow interpretation and prediction of individual responses to drug treatment. For G-protein coupled receptors systematic mutagenesishas provided the major part of functional data as structural information until recently has been very limited. For the pharmacologically important A2A adenosine receptor, extensive site-directed mutagenesisdata on agonist and antagonist binding is available and crystal structures of both types of complexes have been determined. Here, we employ a computational strategy, based on molecular dynamics free energy simulations, to rationalize and interpret available alanine-scanningexperiments for both agonist and antagonist binding to this receptor. These computer simulations show excellent agreement with the experimental data and, most importantly, reveal the molecular details behind the observed effects which are often not immediately evident from the crystal structures. The work further provides a distinct validation of the computational strategy used to assess effects of point-mutationson ligand binding. It also highlights the importance of considering not only protein-ligandinteractions but also those mediated by solvent water molecules, in ligand design projects.