Reaction: ATP + O-phospho-L-serine + tRNACys = AMP + diphosphate + O-phospho-L-seryl-tRNACys
Other name(s): non-canonical O-phosphoseryl-tRNA synthetase; SepRS; O-phosphoseryl-tRNA ligase
Systematic name: O-phospho-L-serine:tRNACys ligase (AMP-forming)
Comments: In organisms like Archaeoglobus fulgidus lacking EC 6.1.1.16 (cysteine—tRNA ligase) for the direct Cys-tRNACys formation, Cys-tRNACys is produced by an indirect pathway, in which EC 6.1.1.27 ligates O-phosphoserine to tRNACys, and EC 2.5.1.73 (O-phospho-L-seryl-tRNA: Cys-tRNA synthase) converts the produced O-phospho-L-seryl-tRNACys to Cys-tRNACys. The SepRS/SepCysS pathway is the sole route for cysteine biosynthesis in the organism [1]. Methanosarcina mazei can use both pathways, the direct route using EC 6.1.1.16 (cysteine—tRNA ligase) and the indirect pathway with EC 6.1.1.27 and EC 2.5.1.73 (O-phospho-L-seryl-tRNA: Cys-tRNA synthase) [2].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
References:
1. Fukunaga, R. and Yokoyama, S. Structural insights into the first step of RNA-dependent cysteine biosynthesis in archaea. Nat. Struct. Mol. Biol. 14 (2007) 272-279. [PMID: 17351629]
2. Hauenstein, S.I. and Perona, J.J. Redundant synthesis of cysteinyl-tRNACys in Methanosarcina mazei. J. Biol. Chem. 283 (2008) 22007-22017. [PMID: 18559341]