Controls on the biosynthesis of the manganese-containing superoxide dismutase of Escherichia coli. Effects of thiols.

In vitro synthesis of Escherichia coli manganese-containing superoxide dismutase, directed by the plasmid pDT1-5, has been achieved. The Mn superoxide dismutase polypeptide was identified by electrophoresis on polyacrylamide gels, immunoprecipitation, and the competitive immunoprecipitation effect of pure, active E. coli Mn superoxide dismutase. Dithiothreitol and glutathione, but not cysteine, suppressed in vitro synthesis of Mn superoxide dismutase. The parallel syntheses of beta-lactamase and of another unidentified polypeptide were not suppressed by thiols. In vitro transcription of the E. coli Mn superoxide dismutase gene was similarly suppressed by glutathione, dithiothreitol, and beta-mercaptoethanol; but not by L-cysteine or thioglycolate. Compounds, such as diamide, 1-chloro-2,4-dinitrobenzene, potassium ferricyanide, and methylene blue, which are expected to deplete intracellular glutathione, caused the induction of Mn superoxide dismutase in anaerobic E. coli.