Inhibition of ribosomal and RNA polymerase functions by rubradirin and its aglycone

The antibiotic rubradirin is structurally related to the ansamycin family of antibiotics. Most members of this group act as specific inhibitors of bacterial RNAP. Rubradirin and its aglycone possess diverging modes of action. Rubradirin inhibits ribosomal functions related to the peptide chain initiation process. It does not inhibit RNAP. By contrast the aglycone of rubradirin retains moderate inhibitory activity towards ribosomal functions but acts essentially as an extremely potent inhibitor of RNAP.