Binding Modes of 2-Phenylamino-6-oxopurines to Herpes Simplex Virus Thymidine Kinases

Federico      Focher; Andrea      Lossani; Andrea      Torti; Joseph      Gambino; George      E. Wright

Abstract

Molecular modelling studies of complexes of 2-phenylamino-6-oxopurines and HSV1 thymidine kinases (TK) revealed two distinct modes of binding. The “acyclovir mode” was occupied by 9R (9-substituted) compounds, and was identical to that revealed by crystal structures of acyclovir and 2-phenylamino-9-(4-hydroxybutyl)-6-oxopurine (HBPG) bound to HSV1 TK. The “base mode” was occupied by 9H compounds such as 2-[3-(trifluoromethyl)phenylamino]-6- oxopurine (m-CF3PG) , and is characterized by rotation of the inhibitor by 180° around the minor axis of the purine ring. In an attempt to understand the molecular basis for affinity of 2-phenylamino-6-oxopurines for TKs, we cloned and expressed site-directed HSV2 TK mutants to create proteins with inhibitor-interacting domains identical with those of HSV1 TK. The enzyme kinetic properties and inhibitory action of several 2-phenylamino-6-oxopurines showed that the changes were not consistently correlated with differences in affinity of inhibitors to the TKs.

Keywords: Thymidine kinase, Molecular modelling, Herpes simplex virus, Inhibitors, acyclovir mode, HBPG, HSV1, HSV2, drug design, strain CL101, strain 333, ATP binding, Crystallization, amino acid, HSV2 mut99, PCR, DNA, Recombinant, Bacterial Cells, IPTG, NaCl, EDTA, radioactivity, Cloning, Mutant, Km, velocity, enzymes, homodimers, AlPG, Arg176, Tyr132, m-CF3PG, QSAR, energy, NH group, TMP, TDP