Identification and synthesis of a naturally occurring selenonucleoside in bacterial tRNAs: 5-[(methylamino)methyl]-2-selenouridine

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Abstract
Escherichia coli, Clostridium sticklandii and Methanococcus vannielii synthesize 75Se-labeled amino acid transfer ribonucleic acids ([75Se]tRNA) when grown with low levels (.apprxeq. 1 .mu.M) of 75SeO32-. When E. coli [75Se]tRNA was digested to nucleosides and analyzed by reversed-phase high-performance liquid chromatography, a single selenonucleoside accounted for 70-90% of the 75Se label in the bulk tRNA. This nucleoside was shown to be indistinguishable in a number of its properties from authentic 5-[(methyl-amino)methyl]-2-selenouridine. Preparation of the authentic selenonucleoside was accomplished and the synthetic compound characterized by its UV and 1H NMR spectral properties. The new selenonucleoside also accounted for 40-60% of the 75Se found in [75Se]tRNA from C. sticklandii or M. vannielii. Each of these anaerobic bacteria contains 1 additional selenonucleoside in their tRNA populations distinct from 5-[(methylamino)methyl]-2-selenouridine. Pure seleno-tRNAGlu isolated from C. sticklandii contains one 5-[(methylamino)methyl]-2-selenouridine and one 4-thiouridine per tRNA molecule.