DNA-dependent RNA polymerase (RNAP) catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Forms the clamp head domain. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Binds at least 2 Zn(2+) per subunit. Part of the 13-subunit RNA polymerase complex (PubMed:19419240, PubMed:21265742, PubMed:22848102). Rpo1N and Rpo5 form a cleft which docks Rpo13. Interacts with Rpo8 on the periphery of the clamp head (PubMed:19419240, PubMed:21265742, PubMed:22848102). Corresponds to about the first two-thirds of the bacterial beta' subunit. Belongs to the RNA polymerase beta' chain family.