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Identification of a selenocysteyl-tRNA(Ser) in mammalian cells that recognizes the nonsense codon, UGA

Journal Article · · J. Biol. Chem.; (United States)
OSTI ID:5722802
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The presence of a unique opal suppressor seryl-tRNA in higher vertebrates which is converted to phosphoseryl-tRNA has been known for several years, but its function has been uncertain. In the present study, we demonstrate that this tRNA species also occurs in vivo as selenocysteyl-tRNA(Ser) suggesting that it functions both as a carrier molecule upon which selenocysteine is synthesized and as a direct selenocysteine donor to a growing polypeptide chain in response to specific UGA codons. (75Se)Seleno(3H)cysteyl-tRNA(Ser) formed by administering 75Se and (3H)serine to rat mammary tumor cells (TMT-081-MS) in culture was isolated from the cell extract. The amino acid attached to the tRNA was identified as selenocysteine following its deacylation and reaction with iodoacetate and 3-bromopropionate. The resulting alkyl derivatives co-chromatographed on an amino acid analyzer with authentic carboxymethylselenocysteine and carboxyethylselenocysteine. Seryl-tRNA(Ser) and phosphoseryl-tRNA(Ser), which co-migrate on a reverse phase chromatographic column with selenocysteyl-tRNA(Ser), were also identified in extracts of TMT-018-MS cells. Hence, we propose that a metabolic pathway for selenocysteine synthesis in mammalian cells is the conversion of seryl-tRNA(Ser) via phosphoseryl-tRNA(Ser) to selenocysteyl-tRNA(Ser). In a ribosomal binding assay selenocysteyl-tRNA(Ser) recognizes UGA but not any of the serine codons. Selenocysteyl-tRNA(Ser) is deacylated more readily than seryl-tRNA(Ser) (i.e. 58% deacylation during 15 min at pH 8.0 and 37 degrees C as compared to 41%).

Research Organization:
National Cancer Institute, Bethesda, MD (USA)
OSTI ID:
5722802
Journal Information:
J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 264:17; ISSN JBCHA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
550901 -- Pathology-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BIOLOGICAL FUNCTIONS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
DISEASES
ELECTRON CAPTURE RADIOISOTOPES
EVEN-ODD NUCLEI
EXPERIMENTAL NEOPLASMS
FUNCTIONS
GLANDS
HYDROXY ACIDS
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIQUID COLUMN CHROMATOGRAPHY
MAMMALS
MAMMARY GLANDS
MESSENGER-RNA
METABOLISM
METALLOPROTEINS
NEOPLASMS
NUCLEI
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
PROTEINS
RADIOISOTOPES
RATS
RIBOSOMES
RNA
RODENTS
SELENIUM 75
SELENIUM ISOTOPES
SEPARATION PROCESSES
SERINE
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TUMOR CELLS
VERTEBRATES