Activity of and Development of Resistance to Corallopyronin A, an Inhibitor of RNA Polymerase

We explored the properties of corallopyronin A (CorA), a poorly characterized inhibitor of bacterial RNA polymerase (RNAP). It displayed a 50% inhibitory concentration of 0.73 mu M against RNAP, compared with 11.5 nM for rifampin. The antibacterial activity of CorA was also inferior to rifampin, and resistant mutants of Staphylococcus aureus were easily selected. The mutations conferring resistance resided in the rpoB and rpoC subunits of RNAP. We conclude that CorA is not a promising antibacterial drug candidate.