A novel DNA gyrase inhibitor rescues Escherichia coli dnaAcos mutant cells from lethal hyperinitiation.
OBJECTIVE
In order to search for novel antibacterial compounds we used a previously developed screening strain designed specifically to discover inhibitors of the bacterial initiator protein, DnaA. This strain (SF53) is not viable at 30 degrees C due to overinitiation. Therefore, compounds that are able to restore growth to SF53 cells are likely to cause either partial or complete inhibition of DnaA function. In this study we used SF53 cells to screen the Library of Pharmacologically Active Compounds (LOPAC).


METHODS
An SF53 screen of LOPAC in 384-well plates was performed. The effects of compounds identified as positive were studied further by growth assays specific for replication proteins as well as an in vitro assay of the activity of purified DNA gyrase.


RESULTS
One of the compounds that tested positive in this screening was the benzazepine derivate (+/-)-6-chloro-PB hydrobromide (S143). We found that the substance did not target DnaA directly, but that it most probably reduces overinitiation by inhibiting DNA gyrase. Benzazepines have not previously been reported as gyrase inhibitors.


CONCLUSIONS
These findings indicate that a screening with SF53 will be able to identify compounds that also target other replication proteins (in addition to DnaA). Screening of LOPAC with SF53 cells led to the discovery of a novel DNA gyrase inhibitor.
Department of Cell Biology, Institute of Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, 0310 Oslo, Norway. line.johnsen@rr-research.no
Line
L
Johnsen
Christoph
C
Weigel
Jens
J
von Kries
Mona
M
Møller
Kirsten
K
Skarstad
D001426:Bacterial Proteins / Q000235:genetics*; D001552:Benzazepines / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors*; D059005:Topoisomerase II Inhibitors
D001426:Bacterial Proteins; D001552:Benzazepines; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D059005:Topoisomerase II Inhibitors