title: Biosynthesis of selenocysteine on its tRNA in eukaryotes.
abstract: 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.
authors.affiliation: Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Xue-Ming
authors.initials: XM
authors.lastname: Xu
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Carlson
authors.forename: Heiko
authors.initials: H
authors.lastname: Mix
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Kazima
authors.initials: K
authors.lastname: Saira
authors.forename: Richard S
authors.initials: RS
authors.lastname: Glass
authors.forename: Marla J
authors.initials: MJ
authors.lastname: Berry
authors.forename: Vadim N
authors.initials: VN
authors.lastname: Gladyshev
authors.forename: Dolph L
authors.initials: DL
authors.lastname: Hatfield
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019843:Archaeal Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D019295:Computational Biology / Q000379:methods; D004151:Dipeptides / Q000378:metabolism; D005057:Eukaryotic Cells / Q000737:chemistry* / Q000201:enzymology; D023281:Genomics / Q000379:methods; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D010766:Phosphorylation; D010768:Phosphoserine / Q000737:chemistry / Q000378:metabolism; D010770:Phosphotransferases / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics* / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D012643:Selenium / Q000737:chemistry / Q000378:metabolism; D017279:Selenocysteine / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014166:Transferases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D004151:Dipeptides; D012346:RNA, Transfer, Amino Acyl; D017279:Selenocysteine; C054334:phosphoseryl-phosphoserine; D010768:Phosphoserine; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D014166:Transferases; D010770:Phosphotransferases; C062762:selenophosphate synthetase; C060600:selenium transferase; D012643:Selenium