Clostridioides difficile RNA polymerase switch region (CdRNAP switch region)

The Clostridioides difficile RNA polymerase switch region is a critical regulatory hinge located at the base of the enzyme's mobile clamp module, primarily formed by the intersection of the beta and beta-prime subunits (Srivastava et al., 2011). This region acts as a mechanical pivot that allows the clamp to open and close, a movement essential for the entry of promoter DNA into the active site channel and the subsequent formation of the open promoter complex during transcription initiation (Boyaci et al., 2018). In the context of Clostridioides difficile infection, this switch region serves as the specific binding site for the macrocyclic antibiotic fidaxomicin (Artsimovitch et al., 2012). By binding to the switch region, fidaxomicin traps the RNA polymerase in a state that cannot initiate transcription, effectively halting the production of bacterial mRNA and proteins (Lin et al., 2018). Because the structural architecture of the bacterial switch region is distinct from that of eukaryotic RNA polymerases, it represents a highly selective target for narrow-spectrum antimicrobial therapy with minimal impact on the host or non-target commensal bacteria (Villain-Guillot et al., 2007). Resistance to drugs targeting this region typically arises through point mutations in the rpoB gene, which alter the binding pocket without compromising essential enzyme function (Leeds et al., 2014).

Other names

RNAP switch regionRNA polymerase clamp baseSwitch region of RNA polymeraseRNAP switch-regionFidaxomicin binding site

Inhibition of transcription initiation by binding to the RNA polymerase switch region and preventing the formation of the open promoter complex (Srivastava et al., 2011).