DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. This subunit often mutates to generate rifampicin (Rif) resistance. Interaction with RbpA partially restores Rif-inhibited transcription; once the subunit is Rif-resistant however RbpA no longer stimulates transcription. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) The RNAP catalytic core consists of 2 alpha, 1 beta, 1 beta' and 1 omega subunit. When a sigma factor is associated with the core the holoenzyme is formed, which can initiate transcription. Interacts with RbpA, which partially restores Rif-inhibited transcription. Mutations in the RRDR sequence (residues 423-449) confer rifampicin (Rif) resistance. Rif blocks transcription inititiation but not elongation. Belongs to the RNA polymerase beta chain family. Truncated N-terminus.