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.
Highlights
From the ‡Section on the Molecular Biology of Selenium, Basic Research Laboratory, NCI, the §Laboratory of Biochemistry, NHLBI, the ʈLaboratory of Molecular Microbiology, NIAID, and the **National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20892
In this report we describe the human 15-kDa protein gene expression as the expression of mRNA inferred from data base analysis, we detected the mouse analog of this human selenoprotein in immunoblot assays in prostate, heart, kidney, spleen, liver, and other mouse organs, with the highest level observed in prostate, suggesting the expression of both mRNA and the selenoprotein in many tissues and cell lines
Concluding Remarks—We have detected a new selenoprotein in human T cells designated as the 15-kDa protein
Summary
From the ‡Section on the Molecular Biology of Selenium, Basic Research Laboratory, NCI, the §Laboratory of Biochemistry, NHLBI, the ʈLaboratory of Molecular Microbiology, NIAID, and the **National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20892. 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.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
