Topoisomerase I, derived from Vaccinia virus, is a type I eukaryotic topoisomerase that removes both positive and negative superhelical turns (also called right- and left-handed supercoils) from covalently closed DNA. The product of the reaction is a covalently closed, circular DNA with fewer positive or negative superhelical turns. DNA Topoisomerase I does not absolutely require Mg2+ to function, although low concentrations of Mg2+ may increase activity.
Studying the effects of supercoiling on transcription in vitro. Studying chromatin reconstitution in vitro. Determining the degree of supercoiling of naturally occurring DNA. Detecting mutant plasmids that differ in length by only one basepair. Increasing restriction endonuclease digestion of resistant DNA substrates by unwinding the DNA coils to expose restriction sites
One unit of DNA Topoisomerase I, Vaccinia, will convert 1 μg of supercoiled DNA (Form I) to relaxed closed circular DNA (Form II) in 1 hour at 37 °C under standard assay conditions.
500 Units; 1000 Units; 5000 Units
50% glycerol containing 50 mM Tris-HCl (pH 7.5), 0.1 M NaCl, 0.1 mM EDTA, 1 mM DTT, and 0.1% Triton® X-100.