PMID:10713132
| Citation |
Zechiedrich, EL, Khodursky, AB, Bachellier, S, Schneider, R, Chen, D, Lilley, DM and Cozzarelli, NR (2000) Roles of topoisomerases in maintaining steady-state DNA supercoiling in Escherichia coli. J. Biol. Chem. 275:8103-13 |
|---|---|
| Abstract |
DNA supercoiling is essential for bacterial cell survival. We demonstrated that DNA topoisomerase IV, acting in concert with topoisomerase I and gyrase, makes an important contribution to the steady-state level of supercoiling in Escherichia coli. Following inhibition of gyrase, topoisomerase IV alone relaxed plasmid DNA to a final supercoiling density (sigma) of -0.015 at an initial rate of 0.8 links min(-1). Topoisomerase I relaxed DNA at a faster rate, 5 links min(-1), but only to a sigma of -0.05. Inhibition of topoisomerase IV in wild-type cells increased supercoiling to approximately the same level as in a mutant lacking topoisomerase I activity (to sigma = -0.08). The role of topoisomerase IV was revealed by two functional assays. Removal of both topoisomerase I and topoisomerase IV caused the DNA to become hyper-negatively supercoiled (sigma = -0.09), greatly stimulating transcription from the supercoiling sensitive leu-500 promoter and increasing the number of supercoils trapped by lambda integrase site-specific recombination. |
| Links | |
| Keywords |
DNA Topoisomerase IV; DNA Topoisomerases, Type I/metabolism; DNA Topoisomerases, Type II/genetics; DNA Topoisomerases, Type II/metabolism; DNA, Bacterial/metabolism; DNA, Superhelical/metabolism; Escherichia coli/enzymology; Escherichia coli/genetics; Models, Genetic; Mutation; Norfloxacin/pharmacology; Plasmids/metabolism; Recombination, Genetic; Topoisomerase II Inhibitors |
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