p1. DNA-dependent RNA polymerase was purified 150-fold from crude extracts of the extreme halophile iHalobacterium cutirubrum/i. 2. The enzyme requires the presence of native DNA and all four nucleoside triphosphates to incorporate sup14/supC-labelled nucleoside triphosphate into an acid-insoluble ribonuclease-sensitive product. 3. It has an absolute requirement for both Mnsup2+/sup and Mgsup2+/sup. 4. The polymerase requires a high salt concentration for stability, but is markedly inhibited by univalent cations. 5. Its molecular weight is very low compared with that of iEscherichia coli/i RNA polymerase./p
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