Specifically methylates position 2 of adenine 2503 in 23S rRNA and position 2 of adenine 37 in tRNAs. m2A2503 modification seems to play a crucial role in the proofreading step occurring at the peptidyl transferase center and thus would serve to optimize ribosomal fidelity. Unmodified tRNA is not a suitable substrate for RlmN, which suggests that RlmN works in a late step during tRNA maturation. adenosine(2503) in 23S rRNA + 2 reduced [2Fe-2S]-[ferredoxin] + 2 S-adenosyl-L-methionine = 2-methyladenosine(2503) in 23S rRNA + 5'-deoxyadenosine + L-methionine + 2 oxidized [2Fe-2S]-[ferredoxin] + S-adenosyl-L-homocysteine adenosine(37) in tRNA + 2 reduced [2Fe-2S]-[ferredoxin] + 2 S-adenosyl-L-methionine = 2-methyladenosine(37) in tRNA + 5'-deoxyadenosine + L-methionine + 2 oxidized [2Fe-2S]-[ferredoxin] + S-adenosyl-L-homocysteine Binds 1 [4Fe-4S] cluster. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. Cells lacking this gene lack nucleoside m2A in both rRNA and tRNAs. Inactivation of rlmN produces an error-prone phenotype since it increases the misreading of a UAG stop codon, and thus decreases translational accuracy. Also leads to increased susceptibility to tiamulin, hygromycin A and sparsomycin. Reaction proceeds by a ping-pong mechanism involving intermediate methylation of a conserved cysteine residue. In details, the methyl group from one SAM molecule is initially transferred to Cys-355 in a typical SN2 displacement. Then a 5'-dA radical formed from a second molecule of SAM abstracts a hydrogen from the methyl group of mCys-355, and the resulting Cys-appended methyl radical attacks the substrate adenine ring. Methyl transfer to C2 thus results in a covalent adduct between the substrate and Cys-355, which is resolved by formation of a disulfide bond between Cys-355 and a second conserved Cys residue (Cys-118). Belongs to the radical SAM superfamily. RlmN family.