Department of Medical Biochemistry and Cell Biology, Göteborg University, SE-405 30 Göteborg, Sweden. maria.falkenberg@medkem.gu.se
In this issue, Lee et al. (2009) present a crystal structure of the human mitochondrial DNA polymerase (POLgamma). The structure of this heterotrimeric enzyme lays a foundation for understanding how POLgamma mutations cause human mitochondrial disease and why some antiviral nucleoside analogs cause cellular toxicity.