text: Biosynthesis of selenocysteine on its tRNA in eukaryotes.
  Selenocysteine (Sec) is cotranslationally inserted into protein in response to UGA codons and is the 21st amino acid in the genetic code. However, the means by which Sec is synthesized in eukaryotes is not known. Herein, comparative genomics and experimental analyses revealed that the mammalian Sec synthase (SecS) is the previously identified pyridoxal phosphate-containing protein known as the soluble liver antigen. SecS required selenophosphate and O-phosphoseryl-tRNA([Ser]Sec) as substrates to generate selenocysteyl-tRNA([Ser]Sec). Moreover, it was found that Sec was synthesized on the tRNA scaffold from selenide, ATP, and serine using tRNA([Ser]Sec), seryl-tRNA synthetase, O-phosphoseryl-tRNA([Ser]Sec) kinase, selenophosphate synthetase, and SecS. By identifying the pathway of Sec biosynthesis in mammals, this study not only functionally characterized SecS but also assigned the function of the O-phosphoseryl-tRNA([Ser]Sec) kinase. In addition, we found that selenophosphate synthetase 2 could synthesize monoselenophosphate in vitro but selenophosphate synthetase 1 could not. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that synthesize selenoproteins.
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entities.type: CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL GENE-Y GENE-N GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y CHEMICAL GENE-Y GENE-Y GENE-N GENE-Y GENE-N GENE-Y GENE-Y GENE-Y CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL
entities.text: O-phosphoseryl selenocysteyl Sec selenide ATP serine seryl O-phosphoseryl selenophosphate Sec Selenocysteine O-phosphoseryl selenophosphate selenocysteine selenophosphate synthetase 1 selenoproteins mammalian Sec synthase SecS soluble liver antigen SecS Sec monoselenophosphate seryl-tRNA synthetase O-phosphoseryl-tRNA([Ser]Sec) kinase selenophosphate synthetase SecS UGA SecS O-phosphoseryl-tRNA([Ser]Sec) kinase selenophosphate synthetase 2 selenophosphate amino acid Sec Sec Sec pyridoxal phosphate selenophosphate