Molecular insights into the mechanism of phenotypic tolerance to rifampicin conferred on mycobacterial RNA polymerase by MsRbpA

Microbiology (Reading). 2011 Jul;157(Pt 7):2056-2071. doi: 10.1099/mic.0.047480-0. Epub 2011 Mar 17.

Abstract

The protein MsRbpA from Mycobacterium smegmatis rescues RNA polymerase (RNAP) from the inhibitory effect of rifampicin (Rif). We have reported previously that MsRbpA interacts with the β-subunit of RNAP and that the effect of MsRbpA on Rif-resistant (Rif(R)) RNAP is minimal. Here we attempted to gain molecular insights into the mechanism of action of this protein with respect to its role in rescuing RNAP from Rif-mediated transcription inhibition. Our experimental approach comprised multiple-round transcription assays, fluorescence spectroscopy, MS and surface plasmon resonance in order to meet the above objective. Based on our molecular studies we propose here that Rif is released from its binding site in the RNAP-Rif complex in the presence of MsRbpA. Biophysical studies reveal that the location of MsRbpA on RNAP is at the junction of the β- and β'-subunits, close to the Rif-binding site and the (i+1) site on RNAP.

MeSH terms

  • Amino Acid Sequence
  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / drug effects
  • Bacterial Proteins / metabolism
  • Binding Sites
  • DNA-Directed RNA Polymerases / antagonists & inhibitors
  • DNA-Directed RNA Polymerases / genetics
  • DNA-Directed RNA Polymerases / metabolism*
  • Mass Spectrometry
  • Mycobacterium smegmatis / drug effects*
  • Mycobacterium smegmatis / genetics
  • Mycobacterium smegmatis / metabolism
  • Protein Binding
  • Protein Subunits / metabolism
  • RNA-Binding Proteins / metabolism
  • Rifampin / metabolism
  • Rifampin / pharmacology*
  • Sequence Alignment
  • Spectrometry, Fluorescence
  • Surface Plasmon Resonance
  • Transcription, Genetic / drug effects*

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Protein Subunits
  • RNA-Binding Proteins
  • DNA-Directed RNA Polymerases
  • Rifampin