SelA, play different roles in Sec synthesis on one tRNA.

Sec (selenocysteine) is biosynthesized on its tRNA and incorporated into selenium-containing proteins (selenoproteins) as the 21st amino acid residue. Selenoprotein synthesis is dependent on Sec tRNA and the expression of this class of proteins can be modulated by altering Sec tRNA expression. The gene encoding Sec tRNA (Trsp) is a single-copy gene and its targeted removal in liver demonstrated that selenoproteins are essential for proper function wherein their absence leads to necrosis and hepatocellular degeneration. In the present study, we found that the complete loss of selenoproteins in liver was compensated for by an enhanced expression of several phase II response genes and their corresponding gene products. The replacement of selenoprotein synthesis in mice carrying mutant Trsp transgenes, wherein housekeeping, but not stress-related selenoproteins are expressed, led to normal expression of phase II response genes. Thus the present study provides evidence for a functional link between housekeeping selenoproteins and phase II enzymes.

GO:0097056 selenocysteinyl-tRNA(Sec) biosynthetic process

selenocysteinyl-tRNA(Sec) biosynthetic process: Ontology: ..

selenocysteinyl-tRNA(Sec) biosynthetic process - …

This tRNA is aminoacylated with a serine in a reaction catalyzed by the enzime seryl-tRNA synthetase (SerS) to generate the base structure for the Sec biosynthesis.

selenocysteinyl-trna(sec) biosynthetic process Antibodies

Key points
• The three-dimensional structure of SelA, the enzyme required for selenocysteine (Sec) synthesis, is determined.
• Four subunits of the huge star-shaped protein, SelA, play different roles in Sec synthesis on one tRNA.
• The findings will contribute to the development of superenzymes by facilitating introduction of selenium (Se) into enzymes.

selenocysteinyl-tRNA(Sec) synthesis: 2011-05-27: Added: SYNONYM: selenocysteinyl-tRNA(Sec…
Furthermore, isopentenylation of tRNA [Ser]Sec was not required for synthesis of Sec on the tRNA

Jovem Revela a Matemática Por Trás de Seus 95% de Acertos.

Warner GJ, Berry MJ, Moustafa ME et al. (2000) Inhibition of selenoprotein synthesis by selenocysteine tRNA[Ser]Sec lacking isopentenyladenosine. Journal of Biological Chemistry 275: 28110–28119.

Overexpression of wild-type tRNA([Ser]Sec) did not affect selenoprotein synthesis.

Selenium, Metamorphosis from Toxin to Essential Mineral

In all Sec-decoding organisms (), the first step in the Sec biosynthetic pathway is the serylation of tRNASec with serine by seryl-tRNA synthetase (). In bacteria, Sec biosynthesis and its incorporation into proteins have been extensively worked out in the nineties (). Selenocysteine synthase (SelA) converts Ser-tRNASec to Sec-tRNASec, which is then incorporated into proteins in the presence of a RNA element (facilitating UGA recognition) and Sec-specific elongation factor SelB (). In Archaea and eukaryotes, Ser-tRNASec is not directly converted to the final product Sec-tRNASec (). Instead, it is first converted to Sep-tRNASec by O-phosphoseryl-tRNA kinase (PSTK) (), and then the resulting tRNA-bound Sep is transformed to Sec by Sep-tRNA:Sec-tRNA synthase (SepSecS) in the presence of selenophosphate (,).

Selenoprotein synthesis is dependent on Sec tRNA and the expression of ..

Methods in cell biology - WormBook

Phylogenetic analysis demonstrated that bacterial, archaeal and eukaryotic selenocysteine incorporation machineries already existed at the time of LUCA () and so did the indirect pathway for cysteine formation (). SepSecS and PSTK are strictly archaeal and eukaryotic enzymes and distinct from the bacterial SelA. The PSTK/SepSecS pathway for synthesizing selenocysteinyl-tRNA is reminiscent of the strictly archaeal tRNA-dependent pathway for cysteine formation in various aspects mentioned earlier. As both SepCysS and SepSecS use tRNA-bound phosphoserine as a substrate, it will be interesting to investigate if the functions of these two enzymes are interchangeable under certain conditions. Considering that most selenoproteins have Cys-containing homologs and a similar genetic code for Sec and Cys (UGA versus UGC/UGU), a dynamic evolutionary relationship may exist between selenocysteine and cysteine ().