EC Explorer

2.1.1.192

23S rRNA (adenine²⁵⁰³-C²)-methyltransferase

(1) 2 S-adenosyl-L-methionine + adenine²⁵⁰³ in 23S rRNA + 2 reduced [2Fe-2S] ferredoxin = S-adenosyl-L-homocysteine + L-methionine + 5′-deoxyadenosine + 2-methyladenine²⁵⁰³ in 23S rRNA + 2 oxidized [2Fe-2S] ferredoxin;;(2) 2 S-adenosyl-L-methionine + adenine³⁷ in tRNA + 2 reduced [2Fe-2S] ferredoxin = S-adenosyl-L-homocysteine + L-methionine + 5′-deoxyadenosine + 2-methyladenine³⁷ in tRNA + 2 oxidized [2Fe-2S] ferredoxin

RlmN, YfgB, Cfr

S-adenosyl-L-methionine:23S rRNA (adenine²⁵⁰³-C²)-methyltransferase

Contains an [4Fe-4S] cluster [2]. This enzyme is a member of the ’AdoMet radical’ (radical SAM) family. S-Adenosyl-L-methionine acts as both a radical generator and as the source of the appended methyl group. RlmN first transfers an CH₂ group to a conserved cysteine (Cys³⁵⁵ in Escherichia coli) [6], the generated radical from a second S-adenosyl-L-methionine then attacks the methyl group, exctracting a hydrogen. The formed radical forms a covalent intermediate with the adenine group of the tRNA [9]. RlmN is an endogenous enzyme used by the cell to refine functions of the ribosome in protein synthesis [2]. The enzyme methylates adenosine by a radical mechanism with CH₂ from the S-adenosyl-L-methionine and retention of the hydrogen at C-2 of adenosine²⁵⁰³ of 23S rRNA. It will also methylate 8-methyladenosine²⁵⁰³ of 23S rRNA. cf. EC 2.1.1.224 [23S rRNA (adenine²⁵⁰³-C⁸)-methyltransferase].

created 2010, modified 2011, modified 2014