2.8.1.15	metabolism	2-Thioribothymidine (s2T) is a modified nucleoside of U, specifically found at position 54 of tRNAs from extreme thermophilic microorganisms. The function of the 2-thiocarbonyl group of s2T54 is thermostabilization of the three-dimensional structure of tRNA	
2.8.1.15	metabolism	The enzyme is required for growth at temperatures above 75°C. Thiolation of thymidine54 in tRNA results in a tRNA molecule with higher thermostability	
2.8.1.15	physiological function	a mutant strain without TtuA activity lacks 2-thioribothymidine in tRNA, exhibits normal growth at an optimal temperature of 7 °C, and shows growth defects at temperatures higher than 80°C	
2.8.1.15	physiological function	mutation of either gene TtuA or TtuB completely abolishes thio-modification of 2-thioribothymidine, and the mutants exhibit a temperature-sensitive phenotype. TtuA is possibly an ATPase possessing a P-loop motif. TtuB is a putative thio-carrier protein. Both TtuA and TtuB are required for 2-thioribothymidine in vitro formation in the presence of cysteine and ATP	
2.8.1.15	physiological function	the sulfur atom of 2-thioribothymidine in tRNA is derived from cysteine or sulfate. Specific 2-thiolation of ribothymidine, at position 54, is observed in vitro, in the presence of ATP. The 2-thiolation reaction in vitro as well as expression of 2-thiolation enzymes in vivo show strong temperature dependence