Conformation of the hypermodified purine queuine: Substrate for the enzyme transfer RNA—guanine transglycosylase

The hypermodified nucleotidyl purine queuine [7-(3,4-trans-4,5-cis-dihydroxycyclopent-1-en-3-ylaminomethyl)-7-deazaguanine] is a substrate for transfer ribonucleic acid (tRNA) enzymes replacing guanine at nucleotide position 34 of tRNAs for the amino acids aspartic acid, asparagine, bistidine and tyrosine. The structure and conformation of native queuine was studied by one-dimensional 13C and 1H NMR spectroscopy and by two-dimensional NMR spectroscopy (COSY and NOESY). The structure in solution was found to be the 3,4-trans-4,5-cis-dihydroxycyclopent-1-ene form. The plane of the cyclopentene ring is probably perpendicular to that of the purine ring structure.