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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Antiviral Agents / chemistry
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Antiviral Agents / pharmacology
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Camptothecin / chemistry
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Camptothecin / pharmacology
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Catalysis
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Catalytic Domain / genetics
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Crystallography, X-Ray
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DNA Topoisomerases, Type I / chemistry*
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DNA Topoisomerases, Type I / genetics
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DNA, Superhelical / chemistry
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DNA, Superhelical / genetics
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DNA, Superhelical / metabolism
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Enzyme Inhibitors / chemistry
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Enzyme Inhibitors / pharmacology
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Models, Molecular
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Mutation / genetics
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Mutation, Missense / genetics
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Nucleic Acid Conformation
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Protein Binding
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Protein Conformation
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Protein Structure, Secondary
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Recombinant Proteins / antagonists & inhibitors
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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Structure-Activity Relationship
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Topoisomerase I Inhibitors
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Variola virus / enzymology*
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Variola virus / genetics
Substances
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Antiviral Agents
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DNA, Superhelical
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Enzyme Inhibitors
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Recombinant Proteins
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Topoisomerase I Inhibitors
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DNA Topoisomerases, Type I
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Camptothecin