Topoisomerase I from vaccinia virus

Enzyme activity is increased in the presence of 2.5 mM Mg²⁺.

Topoisomerase I from vaccinia virus can be used for studying pivotal biological process such as-replication, transcription, recombination as well as DNA structure and topology which includes chromatin reconstitution in vitro and the degree of supercoiling of DNA. Additionally, the product helps in relaxing the DNA coils and exposes the restriction sites which facilitates in enhancing the restriction endonuclease digestion of resistant DNA. It is also used for assaying mutant plasmids which differ in length by only one base-pair.

Topoisomerase I from vaccinia virus also refers as TOPO^®I is a type I DNA topoisomerase, which cleaves DNA at the preferred sequence [5′(C/T)CCTTI]. The product assists in releasing the supercoiling and torsional tension of DNA by cleaving and religating the phosphodiester bonds in a single strand of DNA.

Topoisomerase I relaxes supercoiled DNA molecules. The enzyme initiates transient breakages and rejoins of phosphodiester bonds in superhelical turns of closed-circular DNA. Enzyme activity is independent of right- and left-handed superhelices.

Solution in 50 mM Tris HCl, pH 7.5, containing 100 mM NaCl, 1 mM EDTA, 1 mM DTT, 0.1% Triton X-100, and 50% glycerol.

One unit coverts 1 μg of supercoiled closed circular (Form I) pUC19 DNA to relaxed closed circular form (Form II) in 1 hr at 37 °C.

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