Coordinate and differential in vitro syntheses of two RNA polymerase subunits.

Abstract

THE β subunit of Escherichia coli RNA polymerase—one of three subunit types (α, β, β′) in the enzyme core structure—is specified by a genetic locus, rif(ref. 1). Specialised transducing phages which carry the rif region have been isolated2,3. If DNA is extracted from these phages, it can be used to direct the synthesis of the β subunit in vitro in a coupled transcription/translation system4,5. It has been suggested that other RNA polymerase structural genes may also be in this region of the chromosome6. Recent genetic evidence shows that the β and β′ subunits are produced from a single transcriptional unit in vivo7. DNA extracted from three independently isolated rif transducing phages however, failed to direct the synthesis of any detectable β′ molecules in vitro in the coupled systems previously described4,5 (Fig. 1a). Here I describe a coupled system which synthesises β and β′ in vitro with equal efficiency from rif transducing phage DNA.