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Pathways in De Novo Biosynthesis of Selenocysteine and Cysteine in Eukaryotesстатья
- Авторы: Gladyshev Vadim N., Carlson Bradley A., Hatfield Dolph L.
- Сборник: Selenium
- Место издания: Springer US Boston, MA
- Первая страница: 39
- Последняя страница: 45
- DOI: 10.1007/978-3-319-41283-2_4
- Аннотация: A distinct feature of selenocysteine (Sec) biosynthesis is that this amino acid is synthesized on its tRNA, designated tRNA[Ser]Sec. Sec is then inserted into protein in response to the codon, UGA, as the 21st proteinogenic amino acid. In eukaryotes and archaea, Sec biosynthesis involves several steps. Transfer RNA[Ser]Sec is first aminoacylated by seryl-tRNA synthetase with serine. O-Phosphoseryl-tRNA[Ser]Sec kinase phosphorylates seryl-tRNA[Ser]Sec forming O-phosphoseryl-tRNA[Ser]Sec that in turn reacts with Sec synthase (SEPSECS) in the presence of selenophosphate yielding Sec-tRNA[Ser]Sec. Selenophosphate is generated by selenophosphate synthetase 2 (SPS2) from selenide and/or other selenium metabolites and ATP. Interestingly, sulfide can replace selenide in the reaction involving SPS2 yielding thiophosphate which can then form cysteine- (Cys)-tRNA[Ser]Sec in the presence of SEPSECS. The Cys moiety on Cys-tRNA[Ser]Sec can donate Cys to protein in response to UGA codons at internal positions of mammalian selenoprotein mRNAs. Cys/Sec replacement occurs naturally in vivo and the amount of replacement is dependent on the level of selenium in the diet.
- Добавил в систему: Гладышев Вадим Николаевич