Biomaterial Database

A purified selenophosphate-dependent enzyme from Salmonella typhimurium catalyzes the replacement of sulfur in 2-thiouridine residues in tRNAs with selenium. 1994

Z Veres, and T C Stadtman

Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.

A tRNA-modifying enzyme tentatively termed tRNA 2-selenouridine synthase was purified by a five-step procedure that resulted in 50-60% pure preparations. This enzyme catalyzes the conversion of a 5-methylaminomethyl-2-thiouridine residue in the tRNA substrate to 5-methylaminomethyl-2-selenouridine. The selenium donor substrate for this reaction is shown to be selenophosphate which is formed from ATP and selenide by selenophosphate synthetase. Replacement of sulfur with selenium in tRNAs catalyzed by tRNA 2-selenouridine synthase occurs in the absence of ATP. The dependence of reaction velocity on selenophosphate concentration obeys Michaelis-Menten kinetics indicating an apparent Km value of 17.1 microM. Bulk thio-tRNA preparations from Escherichia coli and Salmonella typhimurium are equally effective as substrates for the selenium incorporation reaction. An intact 3' end of the tRNA molecule does not seem to be essential for selenium incorporation. Identity of the product of the reaction was confirmed by HPLC analysis of digests of [75Se]seleno-tRNAs labeled by incubation with the purified enzyme. A labeled compound in the nucleoside mixture was coeluted with authentic 5-methylaminomethyl-2-selenouridine.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D010710	Phosphates	Inorganic salts of phosphoric acid.	Inorganic Phosphate,Phosphates, Inorganic,Inorganic Phosphates,Orthophosphate,Phosphate,Phosphate, Inorganic
D002850	Chromatography, Gel	Chromatography on non-ionic gels without regard to the mechanism of solute discrimination.	Chromatography, Exclusion,Chromatography, Gel Permeation,Chromatography, Molecular Sieve,Gel Filtration,Gel Filtration Chromatography,Chromatography, Size Exclusion,Exclusion Chromatography,Gel Chromatography,Gel Permeation Chromatography,Molecular Sieve Chromatography,Chromatography, Gel Filtration,Exclusion Chromatography, Size,Filtration Chromatography, Gel,Filtration, Gel,Sieve Chromatography, Molecular,Size Exclusion Chromatography
D002852	Chromatography, Ion Exchange	Separation technique in which the stationary phase consists of ion exchange resins. The resins contain loosely held small ions that easily exchange places with other small ions of like charge present in solutions washed over the resins.	Chromatography, Ion-Exchange,Ion-Exchange Chromatography,Chromatographies, Ion Exchange,Chromatographies, Ion-Exchange,Ion Exchange Chromatographies,Ion Exchange Chromatography,Ion-Exchange Chromatographies
D012329	RNA, Bacterial	Ribonucleic acid in bacteria having regulatory and catalytic roles as well as involvement in protein synthesis.	Bacterial RNA
D012331	RNA, Fungal	Ribonucleic acid in fungi having regulatory and catalytic roles as well as involvement in protein synthesis.	Fungal RNA
D012343	RNA, Transfer	The small RNA molecules, 73-80 nucleotides long, that function during translation (TRANSLATION, GENETIC) to align AMINO ACIDS at the RIBOSOMES in a sequence determined by the mRNA (RNA, MESSENGER). There are about 30 different transfer RNAs. Each recognizes a specific CODON set on the mRNA through its own ANTICODON and as aminoacyl tRNAs (RNA, TRANSFER, AMINO ACYL), each carries a specific amino acid to the ribosome to add to the elongating peptide chains.	Suppressor Transfer RNA,Transfer RNA,tRNA,RNA, Transfer, Suppressor,Transfer RNA, Suppressor,RNA, Suppressor Transfer
D012486	Salmonella typhimurium	A serotype of Salmonella enterica that is a frequent agent of Salmonella gastroenteritis in humans. It also causes PARATYPHOID FEVER.	Salmonella typhimurium LT2
D012644	Selenium Radioisotopes	Unstable isotopes of selenium that decay or disintegrate emitting radiation. Se atoms with atomic weights 70-73, 75, 79, 81, and 83-85 are radioactive selenium isotopes.	Radioisotopes, Selenium
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities