Specific transfer of selenium in selenoprotein biosynthesis

• Published in: Biomedical Research on Trace Elements Vol. 21; no. 4; pp. 187 - 193
• Main Authors: Tobe, Ryuta, Mihara, Hisaaki, Kurihara, Tatsuo, Esaki, Nobuyoshi
• Format: Journal Article
• Language: English; Japanese
• Published: Osaka Japan Society for Biomedical Research on Trace Elements 31.12.2010; 日本微量元素学会; Japan Science and Technology Agency
• Subjects: Biosynthesis; phosphoseryl-tRNA; Selenium; selenocysteine; selenocysteyl-tRNA; selenoprotein
• ISSN: 0916-717X; 1880-1404
• DOI: 10.11299/brte.21.187

Seryl-tRNA synthetase (SerRS) is a class-2 aminoacyl-tRNA synthetase that catalyzes serine activation and its transfer to tRNASer. The enzyme also serylates tRNASec and thus participates in the incorporation of selenocysteine into selenoproteins. Methanogenic archaea possess unusual SerRS evolutionarily distinct from those found in other archaea, eukaryotes, and bacteria. The core three motifs and an active site are conserved in all SerRSs, whereas methanogenic archaeal SerRS has a unique N-terminal domain, which includes a tRNA-binding site. Here, we show evidence that Methanocaldococcus jannaschii seryl-tRNA synthetase (mjSerRS) catalyzes the formation of phosphoseryl-tRNASec (PSer-tRNASec) from serine, tRNASec, and ATP. In vitro analyses revealed that M. jannaschii tRNASec was charged with serine and then converted to PSer-tRNASec by mjSerRS. Furthermore, selenocysteyl-tRNASec (Sec-tRNASec) was synthesized in an in vitro reaction with mjSerRS, selenocysteine synthase, and tRNASec in the absence of seryl-tRNA kinase, which has been proposed as a key enzyme in Sec-tRNASec synthesis in eukaryotes and archaea. Sequence analysis revealed that the N-terminal region of mjSerRS is similar to the entire sequence of M. jannaschii seryl-tRNA kinase. These results suggest that the N-terminus of mjSerRS is responsible for the phosphorylation of seryl-tRNASec.