title: A hydantoin isoform of cyclic N6-threonylcarbamoyladenosine (ct6A) is present in tRNAs.
abstract: N6-Threonylcarbamoyladenosine (t6A) and its derivatives are universally conserved modified nucleosides found at position 37, 3΄ adjacent to the anticodon in tRNAs responsible for ANN codons. These modifications have pleiotropic functions of tRNAs in decoding and protein synthesis. In certain species of bacteria, fungi, plants and protists, t6A is further modified to the cyclic t6A (ct6A) via dehydration catalyzed by TcdA. This additional modification is involved in efficient decoding of tRNALys. Previous work indicated that the chemical structure of ct6A is a cyclic active ester with an oxazolone ring. In this study, we solved the crystal structure of chemically synthesized ct6A nucleoside. Unexpectedly, we found that the ct6A adopted a hydantoin isoform rather than an oxazolone isoform, and further showed that the hydantoin isoform of ct6A was actually present in Escherichia coli tRNAs. In addition, we observed that hydantoin ct6A is susceptible to epimerization under mild alkaline conditions, warning us to avoid conventional deacylation of tRNAs. A hallmark structural feature of this isoform is the twisted arrangement of the hydantoin and adenine rings. Functional roles of ct6A37 in tRNAs should be reconsidered.
authors.affiliation: Institute of Organic Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Matuszewski
authors.affiliation: Institute of General and Ecological Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland.
authors.forename: Jakub
authors.initials: J
authors.lastname: Wojciechowski
authors.affiliation: Department of Chemistry and Biotechnology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Kenjyo
authors.initials: K
authors.lastname: Miyauchi
authors.affiliation: Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
authors.forename: Zofia
authors.initials: Z
authors.lastname: Gdaniec
authors.affiliation: Institute of General and Ecological Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland.
authors.forename: Wojciech M
authors.initials: WM
authors.lastname: Wolf
authors.affiliation: Department of Chemistry and Biotechnology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Institute of Organic Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Sochacka
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006827:Hydantoins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D006827:Hydantoins; D012329:RNA, Bacterial; C003268:N(6)-(N-threonylcarbonyl)adenosine; D012343:RNA, Transfer; D000241:Adenosine