Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
---|---|---|---|---|---|---|
2 S-adenosyl-L-methionine + adenine2503 in 23S rRNA + 2 reduced [2Fe-2S] ferredoxin | Escherichia coli | - |
S-adenosyl-L-homocysteine + L-methionine + 5'-deoxyadenosine + 8-methyladenine2503 in 23S rRNA + 2 oxidized [2Fe-2S] ferredoxin | - |
? |
Organism | UniProt | Comment | Textmining |
---|---|---|---|
Escherichia coli | - |
- |
- |
Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|
2 S-adenosyl-L-methionine + adenine2503 in 23S rRNA + 2 reduced [2Fe-2S] ferredoxin | - |
Escherichia coli | S-adenosyl-L-homocysteine + L-methionine + 5'-deoxyadenosine + 8-methyladenine2503 in 23S rRNA + 2 oxidized [2Fe-2S] ferredoxin | - |
? |
Synonyms | Comment | Organism |
---|---|---|
Cfr | - |
Escherichia coli |
radical S-adenosylmethionine enzyme | - |
Escherichia coli |
Cofactor | Comment | Organism | Structure |
---|---|---|---|
reduced [2Fe-2S] ferredoxin | - |
Escherichia coli | |
S-adenosyl-L-methionine | - |
Escherichia coli |
General Information | Comment | Organism |
---|---|---|
additional information | although SAM is the source of the appended methyl carbon in the reactions catalyzed by RlmN and Cfr, these enzymes operate by a mechanism that is distinctly different from that of typical SAM-dependent methyltransferases. As radical SAM (RS) enzymes, RlmN and Cfr employ very similar radical-based mechanisms of catalysis, initiated by the abstraction of a hydrogen atom from a Cys-appended methyl group via a 5'-deoxyadenosyl 5'-radical. Subsequent attack of the resulting methylene radical upon the carbon atom undergoing methylation affords a protein/RNA cross-linked intermediate whose resolution requires prior proton abstraction from C2 (RlmN) or C8 (Cfr) of the substrate by an unidentified base. Conversion of the intermediate to the methylated product has also been demonstrated in the Cfr reaction. The proximity (5.0 A) of the Cys 355 side chain (the proposed site of thiyl radical formation) to the sulfur atom of Met176, a strictly conserved residue in RlmN and Cfr, might allow formation of a transient thiosulfuranyl radical | Escherichia coli |
physiological function | Cfr modifies C8 of A2503 in 23S rRNA conferring resistance to multiple classes of antibiotics. A2503 is also methylated at C8 by RlmN, which is both evolutionarily and mechanistically related to Cfr. Methylation of C8 of A2503 is the only known in vivo activity of Cfr, while RlmN also installs a C2 methyl group at adenosine 37 | Escherichia coli |