The ␦ protein is a dispensable subunit of Bacillus subtilis RNA polymerase (RNAP) that has major effects on the biochemical properties of the purified enzyme. In the presence of ␦, RNAP displays an increased specificity of transcription, a decreased affinity for nucleic acids, and an increased efficiency of RNA synthesis because of enhanced recycling. Despite these profound effects, a strain containing a deletion of the ␦ gene (rpoE) is viable and shows no major alterations in gene expression.

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... uantitative immunoblotting experiments demonstrate that ␦ is present in molar excess relative to RNAP in both vegetative cells and spores. Expression of rpoE initiates from a single, A -dependent promoter and is maximal in transition phase. A rpoE mutant strain has an altered morphology and is delayed in the exit from stationary phase. For biochemical analyses we have created derivatives of ␦ and A that can be radiolabeled with protein kinase A. Using electrophoretic mobility shift assays, we demonstrate that ␦ binds core RNAP with an apparent affinity of 2.5 ؋ 10 6 M ؊1 , but we are unable to demonstrate the formation of a ternary complex containing core enzyme, ␦, and A .