A model for the mechanism of strand passage by DNA gyrase
AUTOR(ES)
Kampranis, Sotirios C.
FONTE
The National Academy of Sciences
RESUMO
The mechanism of type II DNA topoisomerases involves the formation of an enzyme-operated gate in one double-stranded DNA segment and the passage of another segment through this gate. DNA gyrase is the only type II topoisomerase able to introduce negative supercoils into DNA, a feature that requires the enzyme to dictate the directionality of strand passage. Although it is known that this is a consequence of the characteristic wrapping of DNA by gyrase, the detailed mechanism by which the transported DNA segment is captured and directed through the DNA gate is largely unknown. We have addressed this mechanism by probing the topology of the bound DNA segment at distinct steps of the catalytic cycle. We propose a model in which gyrase captures a contiguous DNA segment with high probability, irrespective of the superhelical density of the DNA substrate, setting up an equilibrium of the transported segment across the DNA gate. The overall efficiency of strand passage is determined by the position of this equilibrium, which depends on the superhelical density of the DNA substrate. This mechanism is concerted, in that capture of the transported segment by the ATP-operated clamp induces opening of the DNA gate, which in turn stimulates ATP hydrolysis.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=17530Documentos Relacionados
- Probing the role of the ATP-operated clamp in the strand-passage reaction of DNA gyrase.
- Mechanism of inhibition of DNA gyrase by cyclothialidine, a novel DNA gyrase inhibitor.
- Recombination of nicked DNA knots by gamma delta resolvase suggests a variant model for the mechanism of strand exchange.
- Micrococcus luteus DNA gyrase: active components and a model for its supercoiling of DNA.
- DNA gyrase action involves the introduction of transient double-strand breaks into DNA.