title: Structural basis for specificity in the poxvirus topoisomerase.
abstract: Although smallpox has been eradicated from the human population, it is presently feared as a possible agent of bioterrorism. The smallpox virus codes for its own topoisomerase enzyme that differs from its cellular counterpart by requiring a specific DNA sequence for activation of catalysis. Here we present crystal structures of the smallpox virus topoisomerase enzyme bound both covalently and noncovalently to a specific DNA sequence. These structures reveal the basis for site-specific DNA recognition, and they explain how catalysis is likely activated by formation of a specific enzyme-DNA interface. Unexpectedly, the poxvirus enzyme uses a major groove binding alpha helix that is not present in the human enzyme to recognize part of the core recognition sequence and activate the enzyme for catalysis. The topoisomerase-DNA complex structures also provide a three-dimensional framework that may facilitate the rational design of therapeutic agents to treat poxvirus infections.
authors.affiliation: University of Pennsylvania School of Medicine, Department of Biochemistry and Biophysics and Howard Hughes Medical Institute, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Kay
authors.initials: K
authors.lastname: Perry
authors.forename: Young
authors.initials: Y
authors.lastname: Hwang
authors.forename: Frederic D
authors.initials: FD
authors.lastname: Bushman
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Van Duyne
mesh_terms: D000998:Antiviral Agents / Q000737:chemistry / Q000494:pharmacology; D002166:Camptothecin / Q000737:chemistry / Q000494:pharmacology; D002384:Catalysis; D020134:Catalytic Domain / Q000235:genetics; D018360:Crystallography, X-Ray; D004264:DNA Topoisomerases, Type I / Q000737:chemistry* / Q000235:genetics; D004278:DNA, Superhelical / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D020125:Mutation, Missense / Q000235:genetics; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D059004:Topoisomerase I Inhibitors; D012901:Variola virus / Q000201:enzymology* / Q000235:genetics
chemical_list: D000998:Antiviral Agents; D004278:DNA, Superhelical; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D059004:Topoisomerase I Inhibitors; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin