The Escherichia coli alkylation response protein AidB is a redox partner of flavodoxin and binds RNA and acyl carrier protein

Microorganisms are exposed to a wide variety of exogenous and endogenous chemical agents that alkylate DNA. Escherichia coli cells exhibit an adaptive response that recognizes and repairs alkylated DNA lesions using Ada, AlkA, and AlkB enzymes. Another alkylation response protein, the DNA-binding flavoprotein AidB, was proposed to repair DNA or protect it from chemical alkylating agents, but direct evidence for its role is lacking. Here, AidB was shown to form tight complexes with both flavodoxin and acyl carrier protein. In addition, electron transfer between 1-electron and 2-electron reduced flavodoxin to oxidized AidB was observed, although with very small rate constants. AidB was found to bind to RNA, raising the prospect that the protein may have a role in protection of RNA from chemical alkylation. Finally, the reagent N-methyl-N′-nitro-N-nitrosoguanidine was eliminated as a direct substrate of the enzyme.