InterPro domain: IPR000541

Cytoplasmic tRNA 2-thiolation protein 1 (also known as Ncs6/Tuc1 in budding yeasts) is responsible for 2-thiolation of mcm5S2U at tRNA wobble positions of tRNA(Lys), tRNA(Glu) and tRNA(Gln) [ 1 , 2 ]. It directly bind tRNAs and probably acts by catalysing adenylation of tRNAs, an intermediate required for 2-thiolation. Its fission yeast homologue, Ctu1 forms a complex with Ctu2 (Ncs2/Tuc2 homologue) and serves as a putative enzyme for the formation of 2-thiouridine [ 3 ]. This family also includes tRNA-5-methyluridine(54) 2-sulfurtransferase, which catalyzes the 2-thiolation of 5-methyluridine residue at position 54 in the T loop of tRNAs, leading to 5-methyl-2-thiouridine [ 4 ].

1. Thio-modification of yeast cytosolic tRNA requires a ubiquitin-related system that resembles bacterial sulfur transfer systems. J. Biol. Chem. 283, 27469-76
2. The conserved Wobble uridine tRNA thiolase Ctu1-Ctu2 is required to maintain genome integrity. Proc. Natl. Acad. Sci. U.S.A. 105, 5459-64
3. Mechanistic characterization of the sulfur-relay system for eukaryotic 2-thiouridine biogenesis at tRNA wobble positions. Nucleic Acids Res. 37, 1335-52
4. Nonredox thiolation in tRNA occurring via sulfur activation by a [4Fe-4S] cluster. Proc. Natl. Acad. Sci. U.S.A. 114, 7355-7360