Aromatic interactions in the binding of ligands to HMGCoA reductase.

3-Hydroxy-3-methyglutaryl-coenzyme A (HMGCoA) reductase is the enzyme that catalyzes the rate-determining step in cholesterol synthesis; it is also the target for statin drugs, which are competitive inhibitors of the enzyme. We examine potentially important enzyme-ligand interactions currently not incorporated into statin drug design: weak, induction/dispersion interactions between ligands and residue tyrosine 479 in the HMGCoA reductase active site. HMGCoA is a large molecule with a long coenzyme A "tail", and in order to study the interactions of interest, it was necessary to find the smallest possible portion of the HMGCoA molecule that would serve as a reasonable model for the entire molecule. Using this minimal model, we calculated BSSE-corrected electronic interaction energies between the residue and the ligand molecule using several DFT methods (local, hybrid, and gradient-corrected DFT methods) as well as MP2. We also performed several in silico mutations of the tyrosine 479 residue to determine the potential effects of these changes on protein-ligand interaction energies. Our work shows that this previously unexploited protein-ligand interaction between tyrosine residue 479 and HMGCoA can be important in the design of future statin drugs. Per our previous work, our results show that local DFT methods more closely match MP2 energy values for aromatic binding than do hybrid or gradient-corrected DFT methods.