Induction of the iron-containing superoxide dismutase in Entamoeba histolytica by a superoxide anion-generating system or by iron chelation.

The regulation of superoxide dismutase (SOD) expression was studied in 4 Entamoeba histolytica isolates. In comparison to anaerobic conditions, cultivation of the amoebae in the presence of superoxide radical anions or a ferrous iron chelator revealed substantial increase of SOD expression. Under the different culture conditions, all SOD activity could be exclusively attributed to an iron-containing type (FeSOD). Northern blot analysis revealed that FeSOD expression was regulated on the transcriptional level. Within the 5'-flanking region of the amoebic FeSOD gene, a 19-bp fragment was found with 68% sequence identity to the consensus motif of the binding site for the ferric uptake regulation gene product of Escherichia coli. Electrophoretic mobility shift assays with this 19-bp fragment and with amoebic nuclear extracts revealed specific DNA/protein complex formation. The results indicate that the regulation of E. histolytica FeSOD expression is similar to that of the manganese-containing SOD (MnSOD) of E. coli.