Biosynthesis and preliminary dynamics of the Y-nucleoside in yeast tRNA/sup Phe/ based on C-13 NMR experiments

Yeast tRNA/sup Phe/ was C-13 enriched (70 atom %) in vivo in methyl groups. Surprisingly, during the authors studies with the C-13 methyl enriched tRNA/sup Phe/, they observed a downfield carbon NMR signal at 120.9 ppm. Carbon spectra of four chemically synthesized Y-base derivatives and Q Base were compared. The authors can now unambiguously assign the downfield signal to C-13 enriched carbon number10 that is added to guanosine to form the third ring in the biosynthesis of Y base. This data encouraged the authors to continue the work on the dynamics of Y in tRNA/sup Phe/. The authors have preliminary NOE data from proton observed carbon decoupled NMR experiments at 500 MHz showing that the N-CH3 methyl of the Y nucleoside exhibited an NOE to C1'-H of its ribose ring and to the C-2H proton of the adjacent adenosine-36 in yeast tRNA/sup Phe/. In conclusion, the presence of the C-13 enriched downfield peak in tRNA/sup Phe/ (C-13 methyl enriched) has yielded new biosynthesis information for the hypermodified nucleoside Y in tRNA. Formation of additional ring most likely starts with methylation of guanosine in position 1. Continued proton observed carbon decoupled NOE experiments will permit us to totally describe the conformation of Y in tRNA/sup Phe/ in solution