5hr6
X-ray crystal structure of C118A RlmN with cross-linked tRNA purified from Escherichia coli
Structural highlights
FunctionRLMN_ECOLI 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.[1] [2] [3] Publication Abstract from PubMedRlmN is a dual-specificity RNA methylase that modifies C2 of adenosine 2503 (A2503) in 23S rRNA and C2 of adenosine 37 (A37) in several Escherichia coli transfer RNAs (tRNAs). A related methylase, Cfr, modifies C8 of A2503 via a similar mechanism, conferring resistance to multiple classes of antibiotics. Here, we report the x-ray structure of a key intermediate in the RlmN reaction, in which a Cys(118)-->Ala variant of the protein is cross-linked to a tRNA(Glu)substrate through the terminal methylene carbon of a formerly methylcysteinyl residue and C2 of A37. RlmN contacts the entire length of tRNA(Glu), accessing A37 by using an induced-fit strategy that completely unfolds the tRNA anticodon stem-loop, which is likely critical for recognition of both tRNA and ribosomal RNA substrates. Crystallographic capture of a radical S-adenosylmethionine enzyme in the act of modifying tRNA.,Schwalm EL, Grove TL, Booker SJ, Boal AK Science. 2016 Apr 15;352(6283):309-12. doi: 10.1126/science.aad5367. PMID:27081063[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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