Transformation of a wobble 2-thiouridine to 2-selenouridine via S-geranyl-2-thiouridine as a possible cellular pathway

•2-Thiouridine is chemically transformed to 2-selenouridine via S-geranyl 2-thiouridine.•This pathway is proposed to be possible in the cell.•It is suggested that SelU may produce geS2U as an intermediate from S2U to Se2U.•2-Selenouridine is characterized by 77Se NMR.

The newly discovered S-geranylated 2-thiouridines (geS2U) (Dumelin et al., 2012) and 2-selenouridines (Se2U) were recently shown to be synthesized by a single enzyme (selenouridine synthase, SelU) through two distinct pathways using the same 2-thiouridine substrate (S2U); however, no clear catalytic mechanism was proposed. We suggest that S-geranyl-2-thiouridine is an intermediate of the SelU-catalyzed conversion of S2U to Se2U. The successful chemical transformation of S2U → geS2U → Se2U is demonstrated here as an initial approximation of the intracellular pathway. The structure of Se2U was confirmed by spectroscopic methods, which included, for the first time, 77Se NMR data (δ 354 ppm).

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