Ganciclovir (GCV) phosphorylation catalysed by the wild type and UL97 mutant proteins (designated by the amino acid change present). Insect cells were infected with the wild type or mutant UL97 expressing baculoviruses at an MOI 10. The medium was supplemented with tritiated GCV at 48 hours. The nucleotides were harvested at 72 hours and bound to DE81 filter paper. The phosphorylated GCV is plotted as percentage phosphorylation compared to the wild type UL97 (set at 100%). Data are the mean +/- one standard deviation of three experiments.