The F plasmid-carried bacterial toxin, the CcdB protein, is known to act on DNA gyrase in two different ways. CcdB poisons the gyrase-DNA complex, blocking the passage of polymerases and leading to double-strand breakage of the DNA. Alternatively, in cells that overexpress CcdB, the A subunit of DNA gyrase (GyrA) has been found as an inactive complex with CcdB. We have reconstituted the inactiv...

In contrast with most bacteria which possess two type II topoisomerases (topoisomerase IV and DNA gyrase), Mycobacterium tuberculosis possesses only one, DNA gyrase, which is functionally a hybrid enzyme. Functional differences between the two type IIA topoisomerases are thought to be specified by a CTD (C-terminal DNA-binding domain), which controls DNA recognition. To explore the molecular me...

Ofloxacin, a potent quinolone antibacterial agent, has a tricyclic ring structure with a methyl group attached to the asymmetric carbon at the C-3 position on the oxazine ring. The S isomer (DR-3355) of ofloxacin has antibacterial activity up to 2 orders of magnitude greater than that of the R isomer (DR-3354). This differential antibacterial activity was not due to different drug transport mec...

The C-terminal domain of the A subunit of DNA gyrase, which we term Gac, is naturally synthesized in Borrelia burgdorferi as an abundant DNA-binding protein. Full-length GyrA, which includes the C-terminal domain, is also synthesized by the spirochete and functions as a subunit of DNA gyrase. We have disrupted synthesis of Gac as an independent protein and demonstrated that it is not essential ...

appearance of bacteria resistant to antibacterial agents puts physicians in trouble and threatens the health of the world. the rapid development of bacterial resistance in escherichia coli to ciprofloxacin makes difficult the treatment of infectious diseases. so, detection of the locations of possible mutations in gyrase a gene ( gyra ) in these mutants is very important to determine the mechan...

The quinolones inhibit the essential bacterial enzymes DNA gyrase and topoisomerase IV, which alter DNA topology after inserting a double-stranded break. DNA gyrase exists as an A2B2 tetramer, encoded by the gyrA and gyrB genes, and catalyses negative DNA supercoiling. Topoisomerase IV exists as a C2E2 tetramer encoded by the parC and parE genes, and is involved in chromosome partitioning. Prev...

Sir, In their recent correspondence, Chu et al. noted the first observation of qnrA3 in salmonellae in Hong Kong, underlining the spread and diversity of plasmidic quinoloneresistance determinants worldwide. Such determinants now include qnrA1–5, qnrB and qnrS, some of which, at least, protect DNA gyrase, as well as the fluoroquinolone-acetylating variant of the aminoglycoside-modifying enzyme ...

Quinolones trap the covalent gyrase-DNA complex in Escherichia coli, leading to cell death. Processing activities for trapped covalent complex have not been characterized. A mutant strain lacking SbcCD nuclease activity was examined for both accumulation of gyrase-DNA complex and viability after quinolone treatment. Higher complex levels were found in ΔsbcCD cells than in wild-type cells after ...