The observation made twenty years ago that type IB topoisomerases bound DNA helix-helix juxtapositions was unexpected, given the controlled helical rotation mechanism of the enzyme. In this issue, Patel et al. (2010) provide an elegant structural explanation for this interaction.
Department of Molecular Virology and Microbiology, Verna and Marrs McClean Department of Biochemistry and Molecular Biology, Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA.
