A new human selenium-containing protein. Purification, characterization, and cDNA sequence

J Biol Chem. 1998 Apr 10;273(15):8910-5. doi: 10.1074/jbc.273.15.8910.

Abstract

Selenium which occurs in proteins as the amino acid, selenocysteine, is essential for numerous biological processes and for human health. A prominent 75Se-labeled protein detected in human T-cells migrated as a 15-kDa band by SDS-polyacrylamide gel electrophoresis. This protein subunit was purified and subjected to tryptic digestion and peptide sequence analyses. Sequences of tryptic peptides derived from the protein corresponded to a human placental gene sequence containing an open reading frame of 162 residues and a readthrough in-frame TGA codon. Three different peptide sequences of the 15-kDa protein corresponded to a nucleotide sequence located downstream of this codon, suggesting that the T-cell 15-kDa selenoprotein contains a selenocysteine residue encoded by TGA. Post-translational processing of the N-terminal portion of the predicted gene product to give the 15-kDa protein was suggested on the basis of molecular mass, amino acid analysis, and immunoblot assays of the purified protein. The 3'-untranslated region (UTR) of the gene encoding the 15-kDa protein contained a sequence that is very similar to the canonical selenocysteine-inserting sequence element. Computer analysis of transcript map data bases indicated that this gene was located on human chromosome 1. Its coding sequence showed no homology to known protein-encoding genes. The 15-kDa protein gene was expressed as mRNA in a wide range of tissues, with increased levels in the thyroid, parathyroid, and prostate-derived cells as evidenced by searches of partial cDNA sequences in public data bases. Genes corresponding to the 15-kDa selenocysteine-containing protein were found in mice and rats, while the corresponding genes in Caenorhabditis elegans and Brugia malayi contained a cysteine codon in place of TGA. The discovery of a new human selenoprotein provides an additional example of the role of selenium in mammalian systems.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Brugia malayi / metabolism
  • Caenorhabditis elegans / metabolism
  • Cell Line
  • Chromosome Mapping
  • Chromosomes, Human, Pair 1
  • DNA, Complementary
  • Gene Library
  • Humans
  • Jurkat Cells
  • Male
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Molecular Weight
  • Neoplasms / metabolism
  • Organ Specificity
  • Peptide Fragments / chemistry
  • Peptide Fragments / isolation & purification
  • Peptide Mapping
  • Protein Biosynthesis*
  • Protein Structure, Secondary*
  • Proteins / chemistry*
  • Proteins / genetics
  • Rats
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Selenium / analysis
  • Selenium / metabolism*
  • Selenium Radioisotopes
  • Selenoproteins
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • T-Lymphocytes / metabolism
  • Transcription, Genetic

Substances

  • DNA, Complementary
  • Peptide Fragments
  • Proteins
  • Recombinant Proteins
  • Selenium Radioisotopes
  • Selenof protein, mouse
  • Selenof protein, rat
  • Selenoproteins
  • Selenium

Associated data

  • GENBANK/AF051894