Fidaxomicin jams Mycobacterium tuberculosis RNA polymerase motions needed for initiation via RbpA contacts

Elife. 2018 Feb 26;7:e34823. doi: 10.7554/eLife.34823.

Abstract

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 identify the structural determinants of Fdx binding to RNAP, we determined 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, explaining its strong effect on M. tuberculosis. Additional structures define conformational states of M. tuberculosis RNAP between the free apo-holoenzyme 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 the Fdx binding pocket.

Keywords: Fidaxomicin; Mycobacterium tuberculosis; RNA polymerase; RbpA; cryo-electron microscopy; molecular biophysics; structural biology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibiotics, Antitubercular / chemistry
  • Antibiotics, Antitubercular / metabolism*
  • Cryoelectron Microscopy
  • DNA-Directed RNA Polymerases / antagonists & inhibitors*
  • DNA-Directed RNA Polymerases / chemistry*
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / metabolism*
  • Fidaxomicin / chemistry
  • Fidaxomicin / metabolism*
  • Models, Molecular
  • Mycobacterium tuberculosis / enzymology*
  • Protein Binding
  • Protein Conformation

Substances

  • Antibiotics, Antitubercular
  • Enzyme Inhibitors
  • DNA-Directed RNA Polymerases
  • Fidaxomicin