Research Spotlight: Structural understanding of viral polymerase inhibition by phosphonoformic acid
Citation: Zahn, K.E., Tchesnokov, E.P., Götte, M., and Doublié S. 2010. Phosphonoformic Acid Inhibits Viral Replication by Trapping the Closed Form of the DNA Polymerase. J Biol Chem. 286:25246-25255.
Karl E. Zahn – is a graduate student in the CMB program
Sylvie Doublié – is a Professor in the MMG Department
Matthias Götte and Egor Tchesnokov are collaborators from McGill University
In this paper, the authors took advantage of a chimeric version of the bacteriophage RB69 DNA polymerase that retained the phosphonoformic acid (PFA) sensitivity of the human cytomegalovirus (HCMV) DNA polymerase but was expressed at levels high enough to pursue structural studies. By comparing the crystal structures of this chimeric polymerase with and without PFA, the authors were able to show that PFA binds to the active site and interacts with two conserved basic residues known to contact the triphosphate tail of incoming nucleotides. The drug also was observed chelating one of the metal ions required for the catalysis by this enzyme. These findings provide a model for the mechanism by which PFA inhibits viral polymerases.
Impact and Significance:
The authors show that PFA inhibits the HCMV chimeric polymerase by trapping the closed, untranslocated form of the polymerase complexed to DNA. Mutational analysis demonstrated that an inter-domain clash biases the chimera toward the closed conformation. This is likely key in the acquired PFA sensitivity and the chimera might aid future drug design targeting HCMV polymerase.