The ATP-operated Clamp of Human DNA Topoisomerase IIα: Hyperstimulation of ATPase by “Piggy-back” Binding
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- 作者：Campbell ; Spencer ; Maxwell ; Anthony
- 关键词：DNA gyrase ; supercoiling ; anti-tumour drugs ; DNA&ndash ; protein interactions ; ADPNP ; 5&prime ; -adenylyl-β ; γ ; -imidodiphosphate ; GyrA ; DNA gyrase A protein ; GyrB ; DNA gyrase B protein ; DMS ; dimethylsuberimidate ; DSG ; disuccinimidyl glutarate ; BS
- 刊名：Journal of Molecular Biology
- 出版年：2002
- 出版时间：July 5, 2002
- 年：2002
- 卷：320
- 期：2
- 页码：171-188
- 全文大小：604 K
文摘
We have constructed a series of clones encoding N-terminal fragments of human DNA topoisomerase IIα. All fragments exhibit DNA-dependent ATPase activity. Fragment 1–420 shows hyperbolic dependence of ATPase on DNA concentration, whereas fragment 1–453 shows hyperstimulation at low ratios of DNA to enzyme, a phenomenon found previously with the full-length enzyme. The minimum length of DNA found to stimulate the ATPase activity was 
10bp; fragments ≥32bp manifest the hyperstimulation phenomenon. Molecular mass studies show that fragment 1–453 is a monomer in the absence of nucleotides and a dimer in the presence of nucleotide triphosphate. The results are consistent with the role of the N-terminal domain of topoisomerase II as an ATP-operated clamp that dimerises in the presence of ATP. The hyperstimulation effect can be interpreted in terms of a “piggy-back binding” model for protein–DNA interaction.
10bp; fragments ≥32bp manifest the hyperstimulation phenomenon. Molecular mass studies show that fragment 1–453 is a monomer in the absence of nucleotides and a dimer in the presence of nucleotide triphosphate. The results are consistent with the role of the N-terminal domain of topoisomerase II as an ATP-operated clamp that dimerises in the presence of ATP. The hyperstimulation effect can be interpreted in terms of a “piggy-back binding” model for protein–DNA interaction.