Joint propagation of the and ' subunits of RNA polymerase in Escherichia coli.

Abstract

The core enzyme of the DNA dependent RNA polymerase from E. coli consists of four subunits, 2α, 1β and 1β′ (ref. 1). The two larger subunits, β and β′, are synthesized in a coordinate manner, possibly on a polycistronic mRNA, in the sequence β before β′ in growing E. coli cells2. The bacteria also have a surplus of these two subunits and, presumably, of the core enzyme at various rates of growth, the number of RNA polymerase molecules being two to five times the number of RNA molecules synthesized by the enzyme3. Assuming a pool of dormant polymerase, the question arises whether the enzyme molecules exchange their subunits while traversing this pool between termination and reinitiation of RNA synthesis as has been described for the protein synthesizing system, the ribosome and its subunits4, or whether the enzyme, once assembled from its subunits, is stable in growing cells. The answer might shed some light on regulation of RNA polymerase activity in vivo.