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The N‐terminus of SECIS Binding Protein 2 is Required for Processive Selenocystine Incorporation in Selenoprotein P
Author(s) -
Pinkerton Mark Hurst,
Vetick Michael,
Shetty Sumangala P,
Copeland Paul R
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.600.9
Subject(s) - selenocysteine , stop codon , selenoprotein , biology , translation (biology) , amino acid , genetics , biochemistry , messenger rna , gene , cysteine , glutathione , glutathione peroxidase , enzyme
A UGA stop codon is recoded to accommodate the incorporation of the 21 st amino acid selenocysteine (Sec). For UGA to be recoded a specialized set of cis and trans factors are required and consist of: an mRNA with an in frame UGA codon, a selenocysteine insertion sequence (SECIS) in the 3′ untranslated region, a SECIS binding protein 2 (SBP2), a specific translation elongation factor (eEFSec), and a selenocysteine tRNA. The N‐terminus of SBP2 is believed to have no direct role in Sec incorporation because the C‐terminus of SBP2 is sufficient for the incorporation of Sec into selenoproteins that have one Sec codon. Having recently developed an in vitro translation system in wheat germ requiring the addition of all Sec‐incorporation factors, we found that translation of SELENOP, which contains 10 Sec codons, is defective in that only early termination products are made. This contrasts with mammalian systems where full length protein is predominantly found. This observation, combined with the fact that neither SELENOP nor the N‐terminus of SBP2 are found in invertebrates, points to a specialized function for the N‐terminus of SBP2 related to SELENOP synthesis. To validate the relationship between the N‐terminus of SBP2 and SELENOP, C‐terminal and full length SBP2 were compared for in vitro translation of SELENOP. We found that the production of full length SELENOP is heavily dependent on the presence of the SBP2 N‐terminus. Our results suggest that the N‐terminus of SBP2 was appended during evolution to allow for processive incorporation of multiple Sec residues into SELENOP. Support or Funding Information This work was supported by National Institutes of Health Grant GM077073