DNA Topoisomerase I

Name: DNA Topoisomerase I
SKU: EMOT1107
Availability: InStock

For research use only. Not intended for any clinical use.

Cat. No. : EMOT1107

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Product Information

Cat. No.	EMOT1107
Description	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.
Concentration	10 U/μl
Applications	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
Size	500 Units; 1000 Units; 5000 Units
Unit Definition	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.
Storage	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.

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Customer Reviews

Customer Q&As

What are the applications of this enzyme?

A: It can be used in studies of the effects of supercoiling on in vitro transcription, in vitro chromatin reconstitution, the degree of supercoiling in naturally occurring DNA, and detection of mutation particles with only a single base pair difference in length.

How is the activity of this enzyme defined?

A: One unit of DNA topoisomerase I is defined as the amount of enzyme that can 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.

Does DNA Topoisomerase I only act on supercoiled molecules of the negative strand?

A: No, this enzyme can cause both positive and negative strand supercoiled molecules to form relaxed forms.

What kind of reactions can this enzyme act on?

A: The enzyme can catalyze four reactions: 1) relaxing supercoils in circular supercoiled DNA molecules, 2) forming and breaking knots within single-stranded circular DNA molecules, 3) catalyzing the formation of double-stranded closed circular DNA molecules from complementary single-stranded circular DNA molecules, and 4) promoting the joining or separation of two circular double-stranded DNA molecules when one of them has a nick in one of its strands.

Why does the gel band size not change after the reaction is completed?

A: After treatment with DNA Topoisomerase I, when running gel electrophoresis with EtBr (bromoethidium), the position of the DNA bands of pBR322 DNA and φX174 DNA RF I (supercoiled molecules) does not change before and after the reaction. This is because the DNA that is converted to a relaxed form by the action of DNA Topoisomerase I is affected by EtBr and becomes supercoiled again. Therefore, after a Topoisomerase I reaction, agarose gel electrophoresis without EtBr is generally used, and EtBr staining is performed after the electrophoresis is completed.

Why does sedimentation occur after the reagent is added during use?

A: When adding 0.1% bovine serum albumin (BSA) directly to 10x buffer, a large amount of white precipitate will be generated. Therefore, when preparing the reaction solution, the reagents need to be added in the following order: dH2O → 10x buffer → 0.1% BSA → substrate DNA.

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Customer Reviews

Magnesium ions are not required

This enzyme, derived from cowpox virus, is a type I eukaryotic topoisomerase with different properties from those of prokaryotic origin and shows activity even in the absence of Mg2+.

United States

2023-01-08

Can be used for a variety of reactions

Can unwind superhelices, form knots and untie knCan unwind superhelices, form knots and untie knots; catalyze the formation of double-stranded closed-loop DNA molecules, linkage reactions of two molecules or reverse reactions.

United States

2023-01-24

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DNA Topoisomerase I

Product Information

Q & A

Customer Reviews

What are the applications of this enzyme?

How is the activity of this enzyme defined?

Does DNA Topoisomerase I only act on supercoiled molecules of the negative strand?

What kind of reactions can this enzyme act on?

Why does the gel band size not change after the reaction is completed?

Why does sedimentation occur after the reagent is added during use?

Magnesium ions are not required

Can be used for a variety of reactions

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