Selenocysteine biosynthesis and insertion machinery in Naegleria gruberi

摘要: Abstract Selenium (Se) is an essential trace element primarily found in selenoproteins as the 21st amino acid (selenocysteine, Sec, or U). Selenoproteins play important role growth and proliferation are typically involved cellular redox balance. Selenocysteine encoded by in-frame UGA codon specified a stem–loop structure, Sec insertion sequence (SECIS), which, eukaryotes, located 3′-untranslated region (UTR). The availability of Naegleria gruberi (ATCC 30224) genome use this organism model system for pathogenic amoeba N. fowleri allowed us to investigate incorporation pathway primitive eukaryote. Using bioinformatics tools, we identified gene sequences encoding PSTK ( O -phosphoseryl-tRNA(Sec) kinase), SepSecS -phosphoseryl-tRNA:selenocysteinyl-tRNA synthase), SelD/SPS2 (selenophosphate synthetase), EFSec (selenocysteine-specific elongation factor) SBP (SECIS binding protein). These findings were confirmed RT-PCR sequencing. A potential tRNA Ser (SelC) putative selenoprotein with similarity mitochondrial thioredoxin reductase (TR3) also identified. Our results show that selenocysteine machinery indeed present . Interestingly, 2214 bp length contains two distinct domains. N-terminal shows predicted methyltransferase proteins, C-terminal homologous prokaryotic SelD/SPS2. suggest possibility novel selenoproteins.