Figure 3.

Effects of PAP I inactivation on functional mRNA stability and protein synthesis in E. coli. The residual capacity of E. coli mRNAs to direct protein synthesis after inhibition of RNA synthesis by rifampicin (rif.) was assessed in the wild-type (pcnB⁺) and pcnB mutant (pcnB⁻) strains. Soluble proteins extracted from cells that were treated with rifampicin for 1, 3, 5, 7 and 9 min and pulse-labelled with radioactive methionine as described in [74] were separated on SDS-polyacrylamide gels. The steady-state level of polypeptides and those synthesized de novo were revealed by Coomassie Blue staining and autoradiography, respectively. The position of GlmS and unknown polypeptides overproduced in the mutant strain are indicated by arrowheads, while the position of an unknown protein overproduced in the wild-type strain is indicated by an asterisk.