EXPLORING THE ACTIVE-SITE OF HERPES-SIMPLEX VIRUS TYPE-1 THYMIDINE KINASE BY X-RAY CRYSTALLOGRAPHY OF COMPLEXES WITH ACYCLOVIR AND OTHER LIGANDS

Antiherpes therapies are principally targeted at viral thymidine kinas es and utilize nucleoside analogs, the triphosphates of which are inhi bitors of viral DNA polymerase or result in toxic effects when incorpo rated into DNA. The most frequently used drug, aciclovir (Zovirax), is a relatively poor substrate for thymidine kinase and high-resolution structural information on drugs and other molecules binding to the tar get is therefore important for the design of novel and more potent che motherapy, both in antiherpes treatment and in gene therapy systems wh ere thymidine kinase is expressed. Here, we report for the first time the binary complexes of HSV-1 thymidine kinase (TK) with the drug mole cules aciclovir and penciclovir, determined by X-ray crystallography a t 2.37 Angstrom resolution. Moreover, from new data at 2.14 Angstrom r esolution, the refined structure of the complex of TK with its substra te deoxythymidine (R = 0.209 for 96% of all data) now reveals much det ail concerning substrate and solvent interactions with the enzyme. Str uctures of the complexes of TK with four halogen-containing substrate analogs have also been solved, to resolutions better than 2.4 Angstrom . The various TK inhibitors broadly fall into three groups which toget her probe the space of the enzyme active site in a manner that no one molecule does alone, so giving a composite picture of active site inte ractions that can be exploited in the design of novel compounds. Prote ins 32:350-361, 1998. (C) 1998 Wiley-Liss, Inc.