Isolation and characterization of inhibitors of the essential histidine kinase, YycG in Bacillus subtilis and Staphylococcus aureus.

The set of sensor kinase YycG and response regulator YycF is the only essential two-component system (TCS) in Bacillus subtilis and Staphylococcus aureus. We have developed a screening method for antibacterial agents that inhibit YycG, the essential histidine kinase (HK). To increase screening sensitivity, a temperature-sensitive yycF mutant (CNM2000) of B. subtilis with super-sensitivity to HK inhibitors was constructed, which was used for the screening of acetone extracts from 4000 microbes. A total of 11 samples showed higher sensitivity to CNM2000 than to wild-type parent 168, and seven of those were characterized to be potent inhibitors against autophosphorylation of YycG. One sample compound was purified and identified as aranorosinol B, a known antibacterial agent against Gram-positive bacteria including B. subtilis and S. aureus. Aranorosinol B inhibited YycG from both B. subtilis and S. aureus with a half-maximum inhibitory concentration (IC50) of 223 and 211 microM, respectively.