THE EFFECTS OF FUR ON THE TRANSCRIPTIONAL AND POSTTRANSCRIPTIONAL REGULATION OF MNSOD GENE (SODA) IN ESCHERICHIA-COLI

Earlier studies have shown that the Fur (ferric uptake regulation) pro tein acts as an anaerobic/aerobic repressor of MnSOD (sodA) expression . We found that the aerobic expression of sodA::lacZ fusion in a Fur(- ) background to be threefold higher than in a Fur(+) background. This effect of fur mutation was not seen in a strain harboring the sodA(+) gene instead of the sodA::lacZ fusion. However, we observed a proporti onate increase in the concentrations of sodA::lacZ and sodA(+) mRNAs i n response to a mutation in the fur gene. These data suggest that the formation of active MnSOD is dependent on a functional fur gene. Indee d, we found that in a fur mutant iron was incorporated into SodA in pl ace of manganese, thus creating inactive and/or partially active forms of the enzyme (i.e., Fe(2)SodA and/or Mn,FeSodA, respectively), resul ting in little or no increase in total MnSOD activity. Thus, Fur plays the role of a repressor at the transcriptional level, but it also pla ys an indirect role at the post-transcriptional level where it affects the maturation of SodA into a fully active enzyme, Mn(2)SodA (MnSOD). (C) 1994 Academic Press, Inc.