Molecular structure and conformation of rifamycin S, a potent inhibitor of DNA-dependent RNA polymerase.

Rifamycins are antibiotics belonging to the group of naphthalenic ansamycins which exert their activity by the specific inhibition of bacterial DNA-dependent RNApolymerase (DDRP)1}. In the presence of active rifamycins, the DDRPonly synthesizes abortive RNA products2). They are produced from Streptomyces mediterranei 3) and are active against a large variety of organisms, such as bacteria, eukaroytes, and viruses, and for that rea-