rpoB

The rpoB gene encodes the β subunit of bacterial RNA polymerase. It is the site of mutations that confer resistance to the rifamycin antibacterial agents, such as rifampin. Mutations in rpoB that confer resistance to rifamycins do so by altering residues of the rifamycin binding site on RNA polymerase, thereby reducing rifamycin binding affinity for rifamycins

Nucleic acid probes can detect mutations in rpoB that confer rifampicin resistance. For Mycobacterium tuberculosis, the rifamycin-resistant mutations most commonly encountered involve codons 516, 526, and 531 (numbered, by convention, as in Escherichia coli rpoB). For Staphylococcus aureus, the rifamycin-resistant mutation most commonly encountered involves codon 526.