Antifungal properties and target evaluation of three putative bacterial histidine kinase inhibitors

Histidine protein kinases have been explored as potential antibacterial dru g targets. The recent identification of two-component histidine kinases in fungi has led us to investigate the antifungal properties of three bacteria l histidine kinase inhibitors (RWJ-49815, RWJ-49968, and RWJ-61907). NI thr ee compounds were found to inhibit growth of the Saccharomyces cerevisiae a nd Candida albicans strains, with MICs ranging from 1 to 20 mu g/ml. Howeve r, deletion of SLN1, the only histidine kinase in S. cerevisiae, did not al ter drug efficacy. In vitro kinase assays were performed by using the Sln1 histidine kinase purified from bacteria as a fusion protein to glutathione S-transferase. RWJ-49815 and RWJ-49968 inhibited kinase a 50% inhibitory co ncentration of 10 mu M, whereas RWJ-61907 failed to inhibit at concentratio ns up to 100 mu M. Based on these results, we conclude that these compounds have antifungal properties; however, their mode of action appears to be in dependent of histidine kinase inhibition.