TI - PHOSphorylation at Asp54 is dispensable for H2O2 resistance mediated by ArcA . AB - Under anaerobic conditions , ArcB is activated by reduced quinones , undergoes auto-phosphorylaTION , and transfers its PHOSphorylation to ArcA [25,32,41-43] . It is not known if ArcA is phosphorylaTED under aerobic conditions or if unPHOSphorylated ArcA has any function . To test if PHOSphorylation is necessary for H2O2 resistance mediated by ArcA , we generated an Asp54 - Ala mutation in ArcA in plasmid pRB3-arcA [38] and used the resulting plasmid pRB3-arcD2A to complement the DeltaarcA mutant E.coli . In H2O2 resistance assays , plasmid pRB3-arcD2A rescued the DeltaarcA mutant E.coli and the resistance of the mutant to H2O2 was restored to the wild type level ( Figure 3 ) . However , unlike the original plasmid pRB3-arcA , plasmid pRB3-arcD2A did not render the complemented DeltaarcA mutant E.coli more resistant to H2O2 than the wild type E.coli ( Figure 3 ) .