Identification of a rhodanese-like protein involved in thiouridine biosynthesis in Thermus thermophilus tRNA.

Incorporation of a sulfur atom into 2-thioribothymidine (s2 T or 5-methyl-2-thiouridine) at position 54 in thermophile tRNA is accomplished by an elaborate system composed of many proteins which confers thermostability to the translation system. We identified ttuD (tRNA-two-thiouridine D) as a gene for the synthesis of s2 T54 in Thermus thermophilus. The rhodanese-like protein TtuD enhances the activity of cysteine desulfurases and receives the persulfide generated by cysteine desulfurases in vitro. TtuD also enhances the formation of thiocarboxylated TtuB, the sulfur donor for the tRNA sulfurtransferase TtuA. Since cysteine desulfurases are the first enzymes in the synthesis of s2 T and other sulfur-containing compounds, TtuD has a role to direct sulfur flow to s2 T synthesis.