Exploring the binding of peptidic West Nile virus NS2B–NS3 protease inhibitors by NMR

Abstract

West Nile virus (WNV) NS2B–NS3 protease is an important drug target since it is an essential protein for the replication of the virus. In order to determine the minimum pharmacophore for protease inhibition, a series of dipeptide aldehydes were synthesized. The 50% inhibitory concentration (IC50) measurements revealed that a simple acetyl-KR-aldehyde was only threefold less active than 4-phenyl-phenylacetyl-KKR-aldehyde (1) (Stoermer et al., 2008) that was used as the reference compound. The ligand efficiency of 0.40kcal/mol/HA (HA=heavy atom) for acetyl-KR-aldehyde is much improved compared to the reference compound 1 (0.23kcal/mol/HA). The binding of the inhibitors was examined using 1H-15N-HSQC experiments and differential chemical shifts were used to map the ligand binding sites. The biophysical studies show that the conformational mobility of WNV protease has a major impact on the design of novel inhibitors, since the protein conformation changes profoundly depending on the structure of the bound ligand.