Structural insight into a quinolone-topoisomerase II-DNA complex. Further evidence for a 2

2 quinobenzoxazine-Mg2+ self-assembly model formed in the presence of topoisomerase II

Yan Kwok, Qingping Zeng, Laurence Hurley

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Quinobenzoxazine A-62176, developed from the anti-bacterial fluoroquinolones, is active in vitro and in vivo against murine and human tumors. It has been previously claimed that A-62176 is a catalytic inhibitor of mammalian topoisomerase II that does not stabilize the cleaved complex. However, at low drug concentrations and pH 6-7, we have found that A-62176 can enhance the formation of the cleaved complex at certain sites. Using a photocleavage assay, mismatched sequences, and competition experiments between psorospermin and A-62176, we pinpointed the drug binding site on the DNA base pairs between positions +1 and +2 relative to the cleaved phosphodiester bonds. A 2:2 quinobenzoxazine-Mg2+ self-assembly model was previously proposed, in which one drug molecule intercalates into the DNA helix and the second drug molecule is externally bound, held to the first molecule and DNA by two Mg2+ bridges. The results of competition experiments between psorospermin and A-62176, as well as between psorospermin and A-62176 and norfloxacin, are consistent with this model and provide the first evidence that this 2:2 quinobenzoxazine-Mg2+ complex is assembled in the presence of topoisomerase II. These results also have parallel implications for the mode of binding of the quinolone antibiotics to the bacterial gyrase-DNA complex.

Original languageEnglish (US)
Pages (from-to)17226-17235
Number of pages10
JournalJournal of Biological Chemistry
Volume274
Issue number24
DOIs
StatePublished - Jun 11 1999
Externally publishedYes

Fingerprint

A 62176
Type II DNA Topoisomerase
Quinolones
Self assembly
Pharmaceutical Preparations
Molecules
DNA
DNA Gyrase
Norfloxacin
Fluoroquinolones
Topoisomerase II Inhibitors
Tumors
Assays
Bacterial DNA
Experiments
Binding Sites
Anti-Bacterial Agents
Base Pairing

ASJC Scopus subject areas

  • Biochemistry

Cite this

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abstract = "Quinobenzoxazine A-62176, developed from the anti-bacterial fluoroquinolones, is active in vitro and in vivo against murine and human tumors. It has been previously claimed that A-62176 is a catalytic inhibitor of mammalian topoisomerase II that does not stabilize the cleaved complex. However, at low drug concentrations and pH 6-7, we have found that A-62176 can enhance the formation of the cleaved complex at certain sites. Using a photocleavage assay, mismatched sequences, and competition experiments between psorospermin and A-62176, we pinpointed the drug binding site on the DNA base pairs between positions +1 and +2 relative to the cleaved phosphodiester bonds. A 2:2 quinobenzoxazine-Mg2+ self-assembly model was previously proposed, in which one drug molecule intercalates into the DNA helix and the second drug molecule is externally bound, held to the first molecule and DNA by two Mg2+ bridges. The results of competition experiments between psorospermin and A-62176, as well as between psorospermin and A-62176 and norfloxacin, are consistent with this model and provide the first evidence that this 2:2 quinobenzoxazine-Mg2+ complex is assembled in the presence of topoisomerase II. These results also have parallel implications for the mode of binding of the quinolone antibiotics to the bacterial gyrase-DNA complex.",
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