RT Journal Article SR Electronic T1 Fidaxomicin jams M. tuberculosis RNA polymerase motions needed for initiation via RbpA contacts JF bioRxiv FD Cold Spring Harbor Laboratory SP 244533 DO 10.1101/244533 A1 Hande Boyaci A1 James Chen A1 Mirjana Lilic A1 Margaret Palka A1 Rachel Anne Mooney A1 Robert Landick A1 Seth A. Darst A1 Elizabeth A. Campbell YR 2018 UL http://biorxiv.org/content/early/2018/01/08/244533.abstract AB Fidaxomicin (Fdx) is an antimicrobial RNA polymerase (RNAP) inhibitor highly effective against Mycobacterium tuberculosis RNAP in vitro, but clinical use of Fdx is limited to treating Clostridium difficile intestinal infections due to poor absorption. To enable structure-guided optimization of Fdx to treat tuberculosis, we report the 3.4 Å cryo-electron microscopy structure of a complete M. tuberculosis RNAP holoenzyme in complex with Fdx. We find that the actinobacteria general transcription factor RbpA contacts fidaxomycin and explains its strong effect on M. tuberculosis. We present additional structures that define conformational states of M. tuberculosis RNAP between the free apo-holenzyme and the promoter-engaged open complex ready for transcription. The results establish that Fdx acts like a doorstop to jam the enzyme in an open state, preventing the motions necessary to secure promoter DNA in the active site. Our results provide a structural platform to guide development of anti-tuberculosis antimicrobials based on Fdx.