Opposite Regulatory Effects of Iron Ions on the In Vitro Catalytic Activities of Nare, the Toxin-like ADP-Ribosyltransferase from Neisseria meningitides

were run in the presence of the iron-chelator O-phenantroline. In the presence of either ferric or ferrous ions there was an increase of the Vmax both for transferase and NADase activity while the Km value for NAD was unaltered. The presence of 10 mM Fe3+ increased the ADP-ribosyltransferase activity when we mutated residues not involved in cluster, while is ineffective when residues involved in cluster are mutated. Similar results were obtained with NAD-glycohydrolase activity. The results presented here demonstrate that iron, which plays an important role in metabolism, can modulate NarE activities depending on its oxidation state. This novel observation could be relevant in the context of Neisseria meningitidis infection.\ud