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the 9th letter of the Roman alphabet (同)i

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iodineの化学記号

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/27 14:03:35」(JST)

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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.

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 supercoils. Together, gyrase and topoisomerase IV remove the positive supercoils that accumulate ahead of a translocating DNA polymerase, allowing DNA replication to continue unhindered by topological strain.

DNA gyrases are analogous enzymes in other organisms.

While topoisomerase IV does relax positive supercoils like DNA gyrase, it does not introduce further negative supercoiling like the latter enzyme.^[1]

Clinical significance

Topoisomerase IV is also a target of antibiotics, such as the quinolone drugs, which include ciprofloxacin.

References

^ Kato J, Suzuki H, and Ikeda H (1992). "Purification and characterization of DNA topoisomerase IV in Escherichia coli". J Biol Chem. 267 (36): 25676–25684. PMID 1334483.

External links

DNA Topoisomerase IV at the US National Library of Medicine Medical Subject Headings (MeSH)

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1. フルオロキノロン類 fluoroquinolones
2. フルオロキノロン類、ドキシサイクリン、およびトリメトプリムスルファメトキサゾール
に対する肺炎レンサ球菌の耐性 resistance of streptococcus pneumoniae to the fluoroquinolones doxycycline and trimethoprim sulfamethoxazole
3. 肺炎連鎖球菌の微生物学および病因 microbiology and pathogenesis of streptococcus pneumoniae

English Journal

Discrepancy between minimal inhibitory concentration to enrofloxacin and mutations present in the quinolone-resistance determining regions of Mycoplasma gallisepticum field strains.

Lysnyansky I, Gerchman I, Levisohn S, Mikula I, Feberwee A, Ferguson NM, Noormohammadi AH, Spergser J, Windsor HM.SourceMycoplasma Unit, Kimron Veterinary Institute, Bet Dagan, Israel. Electronic address: innal@moag.gov.il.
Veterinary microbiology.Vet Microbiol.2012 Nov 9;160(1-2):222-6. doi: 10.1016/j.vetmic.2012.05.002. Epub 2012 May 15.
Molecular characterization of the quinolone-resistance determining regions (QRDRs) of DNA gyrase and topoisomerase IV in 93 Mycoplasma gallisepticum field strains isolated in different geographic regions revealed discrepancies between minimal inhibitory concentration values and presence of amino aci
PMID 22655973

New heterobimetallic Cu(II)-Sn(2)(IV) complex as potential topoisomerase I inhibitor: In vitro DNA binding, cleavage and cytotoxicity against human cancer cell lines.

Tabassum S, Afzal M, Arjmand F.SourceDepartment of Chemistry, Aligarh Muslim University, Aligarh 202 002, India.
Journal of photochemistry and photobiology. B, Biology.J Photochem Photobiol B.2012 Oct 3;115:63-72. Epub 2012 Jul 20.
The new heterobimetallic Cu(II)-Sn(2)(IV)/Ni(II)-Sn(2)(IV) complexes 1 and 2 bearing bioactive pharmacophore ligand scaffold; 1,10-phenanthroline and ethylenediamine were synthesized and characterized by spectroscopic (IR, UV-vis, NMR, ESI-MS) and analytical methods. The in vitro DNA binding studies
PMID 22884481

Japanese Journal

Experimental and Clinical Studies on Fluoroquinolone-insusceptible Escherichia coli Isolated from Patients with Urinary Tract Infections from 1994 to 2007

Wada Koichiro,Kariyama Reiko,Mitsuhata Ritsuko,Uehara Shinya,Watanabe Toyohiko,Monden Koichi,Kumon Hiromi
Acta Medica Okayama 63(5), 263-272, 2009-10
… We analyzed the mutations in quinolone resistance-determining regions of DNA gyrase (gyrA) and topoisomerase IV (parC). …
NAID 120002313204

Synergistic Effect of Kaempferol Glycosides Purified from Laurus nobilis and Fluoroquinolones on Methicillin-Resistant Staphylococcus aureus(Microbiology)

LIU Mei-Hua,OTSUKA Nao,NOYORI Kumiko,SHIOTA Sumiko,OGAWA Wakano,KURODA Teruo,HATANO Tsutomu,TSUCHIYA Tomofusa
Biological & pharmaceutical bulletin 32(3), 489-492, 2009-03-01
In a previous study, we reported that two kaempferol glycosides isolated from Laurus nobilis L., kaempferol-3-O-α-L-(2",4"-di-E p-coumaroyl)-rhamnoside (C2) and kaempferol-3-O-α-L-(2"-E-p-coumaroyl-4" …
NAID 110007122695