This domain of unknown function is often found at the N-terminus of the bacterial tRNA(Met) cytidine acetyltransferase TmcA. TmcA catalyses the formation of N(4)-acetylcytidine (ac4C) at the wobble position of tRNA(Met) by using acetyl-CoA as an acetyl donor and either ATP or GTP [1,2,5]. This modification is thought to ensure precise recognition of the AUG codon by strengthening C-G base-pair interaction and also prevent misrecognition of the near cognate AUA codon [1]. This domain is also found in mammalian N-acetyltransferase 10 (NAT10) and fungal protein Kre33. Kre33 and NAT10 are RNA cytosine acetyltransferases with specificity toward both 18S rRNA and tRNAs and contain additional putative nuclear and nucleolar localization signals (NLS and NoLS respectively) [3,4,5].

1: RNA helicase module in an acetyltransferase that modifies a specific tRNA anticodon. Chimnaronk S, Suzuki T, Manita T, Ikeuchi Y, Yao M, Suzuki T, Tanaka I; EMBO J. 2009;28:1362-1373. PMID:19322199

2: The RNA acetyltransferase driven by ATP hydrolysis synthesizes N4-acetylcytidine of tRNA anticodon. Ikeuchi Y, Kitahara K, Suzuki T; EMBO J. 2008;27:2194-2203. PMID:18668122

3: Yeast Kre33 and human NAT10 are conserved 18S rRNA cytosine acetyltransferases that modify tRNAs assisted by the adaptor Tan1/THUMPD1. Sharma S, Langhendries JL, Watzinger P, Kotter P, Entian KD, Lafontaine DL; Nucleic Acids Res. 2015;43:2242-2258. PMID:25653167

4: RNA cytidine acetyltransferase of small-subunit ribosomal RNA: identification of acetylation sites and the responsible acetyltransferase in fission yeast, Schizosaccharomyces pombe. Taoka M, Ishikawa D, Nobe Y, Ishikawa H, Yamauchi Y, Terukina G, Nakayama H, Hirota K, Takahashi N, Isobe T; PLoS One. 2014;9:e112156. PMID:25402480

5: Recent Advances on the Structure and Function of RNA Acetyltransferase Kre33/NAT10. Sleiman S, Dragon F; Cells. 2019; [Epub ahead of print] PMID:31491951