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Title: RNA helicase module in an acetyltransferase that modifies a specific tRNA anticodon
Authors: Sarin Chimnaronk
Tateki Suzuki
Tetsuhiro Manita
Yoshiho Ikeuchi
Min Yao
Tsutomu Suzuki
Isao Tanaka
Hokkaido University
Mahidol University
University of Tokyo
Keywords: Biochemistry, Genetics and Molecular Biology;Immunology and Microbiology;Medicine;Neuroscience
Issue Date: 6-May-2009
Citation: EMBO Journal. Vol.28, No.9 (2009), 1362-1373
Abstract: Post-transcriptional RNA modifications in the anticodon of transfer RNAs frequently contribute to the high fidelity of protein synthesis. In eubacteria, two genome-encoded transfer RNA (tRNA) species bear the same CAU sequence as the anticodons, which are differentiated by modified cytidines at the wobble positions. The elongator tRNAMet accepts an acetyl moiety at the wobble base to form N4-acetylcytidine (ac4C): an inherent modification ensures precise decoding of the AUG codon by strengthening C-G base-pair interaction and concurrently preventing misreading of the near cognate AUA codon. We have determined the crystal structure of tRNAMet cytidine acetyltransferase (TmcA) from Escherichia coli complexed with two natural ligands, acetyl-CoA and ADP, at 2.35 Å resolution. The structure unexpectedly reveals an idiosyncratic RNA helicase module fused with a GCN5-related N-acetyltransferase (GNAT) fold, which intimately cross-interact. Taken together with the biochemical evidence, we further unravelled the function of acetyl-CoA as an enzyme-activating switch, and propose that an RNA helicase motor driven by ATP hydrolysis is used to deliver the wobble base to the active centre of the GNAT domain.
ISSN: 14602075
Appears in Collections:Scopus 2006-2010

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