Topoisomerase II
| Topoisomerases type II | ||
|---|---|---|
| Identifier | ||
| External IDs |
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| Enzyme classification | ||
| EC, category | 5.99.1.3 , isomerases | |
| Response type | Introduction of double strand breaks, passing a strand through the gap that has arisen, reuniting the strands | |
| Substrate | DNA | |
Topoisomerase II is an enzyme from the group of topoisomerases , which occurs in all organisms and which can loosen and loosen helical turns of double-stranded DNA strands. The bacterial topoisomerase ( gyrase ) is a specialty . It is able to introduce additional turns into a DNA strand. In contrast to topoisomerase I, topoisomerase II requires energy in the form of ATP for its catalytic function .
Two subfamilies can be distinguished:
| Subfamily | Representative members |
| IIA |
|
| IIB | Sulfolobus shibatae ( Archaea ), topoisomerase VI |
The molecular weight of the enzyme is 160–180 kDa , depending on the type of organism . It is a dimeric enzyme that consists of two monomers. A monomer can be divided into three domains : N-terminal domain, central domain and C-terminal domain.
The N-terminal domain consists of approx. 660 amino acids and is used to bind ATP. The central domain consists of approx. 1200 amino acids and contains a tyrosine residue , which is responsible for “cutting up” the DNA. This is also referred to as the catalytic domain. The C-terminal domain varies in length and consists of many charged amino acids. It contains an NLS motif ( Nuclear Localization Signal ). This domain is also partially phosphorylated . The exact function of this domain has not yet been clarified.
In practice, gyrase inhibitors are of particular interest. These are used as antibiotics. The best-known among them include, for example, ciprofloxacin and novobiocin.
Anthracyclines are chemotherapy drugs that are used against various types of cancer , particularly breast cancer . Anthracyclines work by binding to topoisomerase IIα and thus inhibiting cell division.