RNA Polymerase Reaction in Bacteria

Gene expression requires synthesis of a variety of RNAs including protein-coding messenger RNAs (mRNAs), ribosomal RNAs (rRNAs), and transfer RNAs (tRNAs). RNA synthesis is carried out by a protein enzyme called RNA polymerase (RNAP) that proceeds with a unique enzymatic reaction making various products (RNAs) based on DNA template sequences. Bacterial RNAP binds to a specific site of genomic DNA, which is called the promoter DNA, unwinds double-stranded DNA to form the transcription competent open complex (DNA opening), initiates RNA synthesis by nucleotide substrates (de novo or primer-independent transcript initiation), and extends RNA synthesis (transcript elongation) until reaching a termination signal (transcript termination). Transcriptional accuracy of bacterial RNAP is relatively high with an estimated error rate of less than 10^-5, which is achieved by high-fidelity transcription and removing misincorporated nucleotides from RNA (proofreading) by using complex motions of mobile domains around the active site. Transcription is an essential process in bacteria, thereby making RNAP an excellent target for antimicrobial drugs (antibiotics) and some RNAP inhibitors have been used for therapeutic applications.