RpoB

rpoB is the B subunit of the enzyme RNA polymerase. It is the subunit which possesses the polymerase activity, that is, it catalyzes the synthesis of RNA.

This is a highly conserved enzyme contained in many bacteria, including Mycobacterium tuberculosis. It is the target of the antibiotic, Rifampicin. A gene probe for rpoB can detect mutations in the gene that confer rifampicin resistance.

It was initially discovered that resistance to Rifampicin in M. tuberculosis strains was caused by a single point mutation in the rpoB gene. However, recent studies have shown that multiple rpoB mutations in different codons of rpoB can occur.