Induction of Superoxide Dismutases in Escherichia Coli by Manganese and Iron,
DUKE UNIV MEDICAL CENTER DURHAM NC DEPT OF BIOCHEMISTRY
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Growth of Escherichia coli B in simple media enriched with MnII resulted in the elevation of the manganese-containing superoxide dismutase, whereas growth in such medium enriched with iron caused increased content of the iron-containing superoxide dismutase. Enrichment of the medium with CoII, CuII, MoVI, ZnII, or NiII had no effect. The inductions of superoxide dismutase by MnII or by FeII were dioxygen dependent, but these metals did not affect the CN- resistant respiration of E. coli B and did not influence the increase in the CN- resistant respiration caused by paraquart. MnII reduced the growth inhibition imposed by paraquat. E. coli grown in the complex 3 Trypticase soy broth NNL Microbiology Systems- 0.5 yeast extract-0.2 glucose medium contained more superoxide dismutase than did cells grown in the simple media and were less responsive to enrichment of the medium with MnII or FeII. Nevertheless, in the presence of paraquat, inductions of superoxide dismutase by these metals could be seen even in the Trypticase-yeast extract- glucose medium. On the basis of these observations we propose that the apo- superoxide dismutases may act as autogenous repressors and that MnII and FeII increase the cell content of the corresponding enzymes by speeding the conversion of the apo- to the holoenzymes. Originator-supplied key words include Superoxide dismutases, Escherichia coli, Manganese, Iron.