>1 Form Enzym

Upon growth transition of Escherichia coli cells from exponential to stationary phase, RNA polymerase is converted into at least three different forms (S1, S2 and S3), which could be separately isolated by phosphocellulose column chromatography (Ozaki et al., 1991 (2)). Mere, the promoter selectivity of these three stationary-phase enzymes was examined using an in vitro mixed transcription system and an E.coli promoter collection. These altered forms of RNA polymerase showed different recognition properties of promoters from that by the log-phase holoenzyme (L1). One of the stationary-phase RNA polymerases, S1, was found to be converted in vitro into an enzyme like the log-phase form following incubation with nucleotides or pyrophosphate. The conversion was indicated by not only the shift of elution position from a phosphocellulose column but also the change in the promoter selectivity. These results may suggest that RNA polymerase is interconvertible between different forms with different promoter selectivity by interaction with a phosphorylated compound(s).