A selenium-containing nucleoside at the first position of the anticodon in seleno-tRNA(Glu) from Clostridium sticklandii

Abstract

In previous studies, the single selenonucleoside component of a selenium-containing tRNA(Glu) isolated from Clostridium sticklandii has been shown to be 5-methyl-aminomethyl-2-selenouridine. Here, we show that this selenonucleoside is most likely located at the 'wobble' position of the anticodon of the clostridial seleno-tRNA(Glu). Nuclease T1 digestion of this seleno-tRNA(Glu) generated one major selenium-containing oligonucleotide (25 bases long). The selenium-containing residue within this oligonucleotide was located by sequence analysis of the oligonucleotide before and after removal of selenium by treatment with cyanogen bromide. The sequence of this oligonucleotide, A-A-C-C-G-C-C-C-U-U+-U-C-A+C-G-G-C-G-G-U-A-A-C-A-G, is homologous to that of the Escherichia coli tRNA2(Glu) from residues 27 to 50, including the anticodon region and the variable loop, except that the E. coli tRNA has 5-methylaminomethyl-2-thiouridine instead of the selenonucleoside.