Gammaherpesviruses encode functional dihydrofolate reductase activity.
We overexpressed and purified from Escherichia coli the dihydrofolate reductase (DHFR) of the gammaherpesviruses human herpesvirus 8 (HHV-8), herpesvirus saimiri (HVS), and rhesus rhadinovirus (RRV). All three enzymes proved catalytically active. The K(m) value of HHV-8 DHFR for dihydrofolate (DHF) was 2.02+/-0.44 microM, that of HVS DHFR was 4.31+/-0.56 microM, and that of RRV DHFR is 7.09+/-0.11 microM. These values are approximately 5-15-fold higher than the K(m) value reported for the human DHFR. The K(m) value of HHV-8 DHFR for NADPH was 1.31+/-0.23 microM, that of HVS DHFR was 3.78+/-0.61 microM, and that of RRV DHFR was 7.47+/-0.59 microM. These values are similar or slightly higher than the corresponding K(m) value of the human enzyme. Methotrexate, aminopterin, trimethoprim, pyrimethamine, and N(alpha)-(4-amino-4-deoxypteroyl)-N(delta)-hemiphthaloyl-L-ornithine (PT523), all well-known folate antagonists, inhibited the DHFR activity of the three gammaherpesviruses competitively with respect to DHF but proved markedly less inhibitory to the viral than towards the human enzyme.
D000818:Animals; D003001:Cloning, Molecular; D003587:Cytomegalovirus / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology; D018142:Gammaherpesvirinae / Q000201:enzymology* / Q000235:genetics; D019288:Herpesvirus 8, Human / Q000201:enzymology / Q000235:genetics; D006801:Humans; D007700:Kinetics; D051379:Mice; D011994:Recombinant Proteins / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics* / Q000378:metabolism
D011994:Recombinant Proteins; D013762:Tetrahydrofolate Dehydrogenase