A form of the DNA-dependent RNA polymerase of Halobacterium halobium, containing an additional component, is able to transcribe native DNA.

A revised procedure for the purification of DNA-dependent RNA polymerase from Halobacterium halobium, including two-phase partition, yields pure, highly active and absolutely DNA-dependent enzyme. Two forms of the enzyme, one containing, the other not containing a previously not observed component, epsilon, show striking differences in activity. RNA polymerase without component epsilon has a significant activity on poly[d(A-T)] but only insignificant activity on all other templates. The enzyme containing a stoichiometric amount of component epsilon transcribes poly[d(A-T)] and native templates efficiently.