Escherichia coli DNA topoisomerase I mutants: Increased supercoiling is corrected by mutations near gyrase genes |
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Authors: | Gail J. Pruss Stephen H. Manes Karl Drlica |
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Affiliation: | Department of Biology University of Rochester Rochester, New York 14627 USA |
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Abstract: | Bacterial chromosomes and plasmid (pBR322) DNA from topoisomerase I-defective Escherichia coli strains have been characterized with respect to superhelical density. The topoisomerase I defect results in increased negative superhelical density of both the bacterial chromosome and pBR322. Thus topoisomerase I is involved in determining the level of supercoiling in bacteria. Three of the topoisomerase I-defective strains we studied carry secondary mutations that decrease superhelical density; these additional mutations are closely linked to the gyrB locus in two of the strains and to the gyrA locus in the third strain. |
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