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Lethal fragmentation of bacterial chromosomes mediated by DNA gyrase and quinolones
Author(s) -
Malik Muhammad,
Zhao Xilin,
Drlica Karl
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05275.x
Subject(s) - dna gyrase , nalidixic acid , biology , quinolone , repressor lexa , dna , escherichia coli , circular bacterial chromosome , nucleoid , holliday junction , microbiology and biotechnology , dna replication , biochemistry , dna repair , repressor , gene , antibiotics , transcription factor
Summary When DNA gyrase is trapped on bacterial chromosomes by quinolone antibacterials, reversible complexes form that contain DNA ends constrained by protein. Two subsequent processes lead to rapid cell death. One requires ongoing protein synthesis; the other does not. The prototype quinolone, nalidixic acid, kills wild‐type Escherichia coli only by the first pathway; fluoroquinolones kill by both. Both lethal processes correlated with irreversible chromosome fragmentation, detected by sedimentation and viscosity of DNA from quinolone‐treated cells. However, only fluoroquinolones fragmented purified nucleoids when incubated with gyrase purified from wild‐type cells. A GyrA amino acid substitution (A67S) expected to perturb a GyrA–GyrA dimer interface allowed nalidixic acid to fragment chromosomes and kill cells in the absence of protein synthesis; moreover, it made a non‐inducible lexA mutant hypersusceptible to nalidixic acid, a property restricted to fluoroquinolones with wild‐type cells. The GyrA variation also facilitated immunoprecipitation of DNA fragments by GyrA antiserum following nalidixic acid treatment of cells. The ability of changes in both gyrase and quinolone structure to enhance protein synthesis‐independent lethality and chromosome fragmentation is explained by drug‐mediated destabilization of gyrase–DNA complexes. Instability of type II topoisomerase–DNA complexes may be a general phenomenon that can be exploited to kill cells.