Synthesis of 5-methylaminomethyl-2-selenouridine in tRNAs: 31P NMR studies show the labile selenium donor synthesized by the selD gene product contains selenium bonded to phosphorus

Z. Veres, L. Tsai, T. D. Scholz, M. Politino, R. S. Balaban, T. C. Stadtman

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Abstract

An enzyme preparation from Salmonella typhimurium catalyzes the conversion of 5-methylaminomethyl-2-thiouridine in tRNAs to 5-methylaminomethyl-2- selenouridine when supplemented with selenide and ATP. Similar preparations from a Salmonella mutant strain carrying a defective selD gene fail to catalyze this selenium substitution reaction. However, supplementation of the deficient enzyme preparation with the purified selD gene product (SELD protein) restored synthesis of seleno-tRNAs. In the absence of the complementary enzyme(s), the SELD protein catalyzes the synthesis of a labile selenium donor compound from selenide and ATP. 31P NMR studies show that among the products of this reaction are AMP and a compound containing selenium bonded to phosphorus. The reaction is completely dependent on the addition of both selenide and magnesium. The dependence of reaction velocity on ATP concentration shows sigmoidal kinetics, whereas dependence on selenide concentration obeys Michaelis-Menten kinetics indicating a K(m) value of 46 μM for selenide.

Original languageEnglish
Pages (from-to)2975-2979
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume89
Issue number7
DOIs
Publication statusPublished - Jan 1 1992

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Keywords

  • seleno-tRNAs
  • selenophosphate

ASJC Scopus subject areas

  • General

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