Type II topoisomerase

Type II topoisomerase is a type of enzyme that manipulates the topological states of DNA by passing an intact double helix through a transient break which it generates in another. This enzyme is essential for DNA replication and transcription, and is a target for several antibacterial and anticancer drugs.

Function

Type II topoisomerases are able to change the DNA topology by creating transient double-strand breaks in the DNA, through which another double-stranded DNA segment is passed. This allows the enzyme to increase or decrease the linking number of DNA in steps of two. The enzyme is also capable of relaxing supercoiled DNA, unknotting or decatenating intertwined DNA molecules.

Structure

Type II topoisomerases are multimeric enzymes, composed of multiple subunits. They have a common core structure, which includes a breakage-reunion domain, a DNA cleavage site, and an ATPase domain. The ATPase domain is responsible for the energy-dependent strand passage mechanism of the enzyme.

Clinical significance

Type II topoisomerases are targets for several antibacterial and anticancer drugs. These drugs function by stabilizing the transient break in the DNA created by the enzyme, leading to DNA damage and cell death. Examples of such drugs include quinolones, which are used as antibacterials, and etoposide and doxorubicin, which are used as anticancer drugs.

See also

• Topoisomerase
• DNA replication
• Transcription (genetics)
• Quinolones
• Etoposide
• Doxorubicin

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