ADP-ribosylation as an intermediate step in inactivation of rifampin by a mycobacterial gene

Mycobacterium smegmatis DSM43756 inactivates rifampin, and the inactivated antibiotic product recovered from culture medium was ribosylated on the 23- OH group. To study this process, the gene responsible for the inactivation was expressed at high levels by the lac promoter in Escherichia coli confer ring resistance to >500 mu g of antibiotic per mi. Cell homogenates generat ed a novel derivative designated RIP-TAs; in this study, we determined that RIP-TAs is 23 (O-ADP-ribosyl)rifampin. Our results indicated that RIP-TAs is an intermediate in the pathway leading to ribosylated rifampin and that the previously characterized gene encodes a mono(ADP-ribosyl)transferase wh ich, however, shows no sequence similarity to other enzymes of this class.