2.5.1.73	additional information	two-step Cys-tRNACys formation: in organisms like Archaeoglobus fulgidus lacking a canonical cysteinyl-tRNA synthetase for the direct Cys-tRNACys formation, Cys-tRNACys is produced by the indirect pathway, in which the non-canonical O-phosphoseryl-tRNA synthetase, SepRS, ligates the non-canonical amino acid O-phosphoserine, Sep, to tRNACys, and the Sep-tRNA:Cys-tRNA synthase converts the produced Sep-tRNACys to Cys-tRNACys, overview, the SepRS/SepCysS pathway is the sole route for cysteine biosynthesis in the organism	Archaeoglobus fulgidus	?	-	?	89	
2.5.1.73	additional information	the active site contains an internal aldimine Lys209-PLP and the sulfate ion, SepCysS should not bind Sep-tRNASec and discriminate tRNACys from tRNASec on the basis of the differences in the length of the T-arms, or SepCysS recognizes the discriminator sequence, which is Ura73 in tRNACys and Gua73 in tRNASec, overview	Archaeoglobus fulgidus	?	-	?	89	
2.5.1.73	additional information	thiosulfate shows 72.6% of the activity compared to sulfide as sulfur donor, cysteine shows 77% of the activity compared to sulfide as sulfur donor. No correct Cys-tRNACys product is formed in presence of these sulfur donors	Methanosarcina mazei	?	-	?	89	
2.5.1.73	additional information	the highly conserved Cys residues Cys64, Cys67, and Cys272 are essential for the sulfhydrylation reaction in vivo. Cys64 and Cys67 form a disulfide linkage and carry a sulfane sulfur in a portion of the enzyme, suggesting that a persulfide group containing a sulfane sulfur is the proximal sulfur donor for cysteine biosynthesis. The presence of Cys272 increases the amount of sulfane sulfur in the enzyme by 3fold, suggesting that this Cys residue facilitates the generation of the persulfide group. A sulfur relay mechanism recruits both disulfide and persulfide intermediates	Methanocaldococcus jannaschii	?	-	?	89	
2.5.1.73	additional information	the highly conserved Cys residues Cys64, Cys67, and Cys272 are essential for the sulfhydrylation reaction in vivo. Cys64 and Cys67 form a disulfide linkage and carry a sulfane sulfur in a portion of the enzyme, suggesting that a persulfide group containing a sulfane sulfur is the proximal sulfur donor for cysteine biosynthesis. The presence of Cys272 increases the amount of sulfane sulfur in the enzyme by 3fold, suggesting that this Cys residue facilitates the generation of the persulfide group. A sulfur relay mechanism recruits both disulfide and persulfide intermediates	Methanocaldococcus jannaschii DSM 2661	?	-	?	89	
2.5.1.73	O-phospho-L-seryl-tRNACys + sulfate	-	Methanospirillum hungatei	L-cysteinyl-tRNACys + phosphate	-	?	386637	
2.5.1.73	O-phospho-L-seryl-tRNACys + sulfate	-	Methanopyrus kandleri	L-cysteinyl-tRNACys + phosphate	-	?	386637	
2.5.1.73	O-phospho-L-seryl-tRNACys + sulfate	-	Archaeoglobus fulgidus	L-cysteinyl-tRNACys + phosphate	-	?	386637	
2.5.1.73	O-phospho-L-seryl-tRNACys + sulfate	-	Methanococcoides burtonii	L-cysteinyl-tRNACys + phosphate	-	?	386637	
2.5.1.73	O-phospho-L-seryl-tRNACys + sulfate	evolutionary history of Cys-tRNACys formation, overview	Methanospirillum hungatei	L-cysteinyl-tRNACys + phosphate	-	?	386637