A new human selenium-containing protein. Purification, characterization, and cDNA sequence.
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.
Gladyshev
V N
VN
Section on the Molecular Biology of Selenium, Basic Research Laboratory, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.VNG@unlinfo2.unl.edu
Jeang
K T
KT
Wootton
J C
JC
Hatfield
D L
DL
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017178:Brugia malayi / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000378:metabolism; D002460:Cell Line; D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1; D018076:DNA, Complementary; D015723:Gene Library; D006801:Humans; D019169:Jurkat Cells; D008297:Male; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009369:Neoplasms / Q000378:metabolism; D009928:Organ Specificity; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010449:Peptide Mapping; D014176:Protein Biosynthesis; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012643:Selenium / Q000032:analysis / Q000378:metabolism*; D012644:Selenium Radioisotopes; D051140:Selenoproteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000378:metabolism; D014158:Transcription, Genetic
D018076:DNA, Complementary; D010446:Peptide Fragments; D011506:Proteins; D011994:Recombinant Proteins; D012644:Selenium Radioisotopes; C495239:Selenof protein, mouse; C495241:Selenof protein, rat; D051140:Selenoproteins; D012643:Selenium