W0413

Structural Basis for the Diphosphorylation Activity of EHV4-TK and HSV1-TK. Anna Gardberg, Arnon Lavie, Ludmilla Shuvalova, Christian Monnerjahn, Manfred Konrad, Biochemistry and Molecular Biology, UIC, 1819 W. Polk St. MC 536, Chicago, IL 60612 USA.

For suicide gene therapy, equine herpesvirus type 4 thymidine kinase (EHV4-TK) has more activity toward prodrugs than HSV1-TK. The crystal structures of EHV4-TK in complex with a) THY and ADP b) THY and SO₄ c) TP₄A and d) TP₅A have been solved by molecular replacement. Additionally, the structure of HSV1-TK in complex with TP₅A has been solved. While the active sites of HSV1-TK and EHV4-TK resemble one another, notable differences are observed in the LID regions and in the way the base of the phosphoryl-acceptor molecule is bound. The latter difference could explain the higher activity of EHV4-TK toward the prodrug gancyclovir (GCV).