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Dna Topoisomerase Iv
Topoisomerase IV is one of two Type II topoisomerases in bacteria, the other being DNA gyrase. Like gyrase, topoisomerase IV is able to pass one double-strand of DNA through another double-strand of DNA, thereby changing the linking number of DNA by two in each enzymatic step. Both share a hetero-4-mer structure formed by a symmetric homodimer of A/B heterodimers, usually named ''ParC'' and ''ParE''. Functions Topoisomerase IV has two functions in the cell. * First, it is responsible for unlinking, or decatenating, DNA following DNA replication. The double-helical nature of DNA and its semiconservative mode of replication causes the two newly replicated DNA strands to be interlinked. These links must be removed in order for the chromosome (and plasmids) to segregate into daughter cells so that cell division can complete. * Topoisomerase IV's second function in the cell is to relax positive supercoils. It shares this role with DNA gyrase, which is also able to relax positive superco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type II Topoisomerase
Type II topoisomerases are topoisomerases that cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils. They use the hydrolysis of ATP, unlike Type I topoisomerase. In this process, these enzymes change the linking number of circular DNA by ±2. Topoisomerases are ubiquitous enzymes, found in all living organisms. In animals, topoisomerase II is a chemotherapy target. In prokaryotes, gyrase is an antibacterial target. Indeed, these enzymes are of interest for a wide range of effects. Function Type II topoisomerases increase or decrease the linking number of a DNA loop by 2 units, and it promotes chromosome disentanglement. For example, DNA gyrase, a type II topoisomerase observed in '' E. coli'' and most other prokaryotes, introduces negative supercoils and decreases the linking number by 2. Gyrase is also able to remove knots from the bacterial chromosome. Along with gyrase, most prokaryotes also contain a second type IIA topoisomerase, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
