Localisation of a Region on Subunit B' Neighboring the Active Center of the RNA Polymerase from Methanobacterium thermoautotrophicum Strain W

The immediate neighborhood of the active center of the DNA-directed RNA polymerase from the archaebacterium Methanobacterium thermoautotrophicum is radioactively labeled upon incubation of the enzyme with one of 15 different chemically reactive nucleotide analogs which function as initiating substrate and with [α-33PJUTP as elongating substrate in presence of poly[d(A-T)J as template. All analogs lead to the labeling of subunit B′. With analogs containing an alkyl chloride as the chemically reactive group, subunit B″ also becomes labeled. This suggests that regions of subunit B″ must also be located close to the active center. In the case of subunit B′ the label is attached between tyr273 and met383. Comparison of the amino acid sequence of the labeled region with that of labeled regions in RNA polymerase from other sources indicates a strong conservation of the active center during evolution.