Structure of a modified nucleoside in archaebacterial tRNA which replaces ribosylthymine. 1-Methylpseudouridine

The structure of a modified nucleoside isolated from Halococcus morrhuae tRNA has been established as 1-methylpseudouridine, based on mass spectrometry and gas chromatography carried out on 0.2 A260 unit of material. Not previously found in nucleic acids, 1-methylpseudouridine appears to be unique to archaebacterial tRNA, where it replaces ribosylthymine in the T psi C loop of most of the tRNAs examined thus far.