EFFECT OF LANTHANUM IONS ON TRNA(PHE) STRUCTURE - IMINO PROTON NMR-SPECTROSCOPY

The effect of lanthanum ions on the structural and conformational chan ge of yeast tRNA(Phe) was studied by H-1 NMR. The results suggest that the tertiary base pair (G-15)(C-48), which was located in the termina l in the augmented dihydrouridine helix (D-helix), was markedly affect ed by adding La3+ and shifted 0.33 downfield. Based pair (U-8)(A-14), which is associated with a tertiary interaction, links the base of the acceptor stem to the D-stem and anchors the elbow of the L structure, shifted 0.20 upfield. Another imino proton that may be affected by La 3+ in tRNA(Phe) is the tertiary base pair (G-19)(C-56). The assignment of this resonance is tentative since it is located in the region of h ighly overlapping resonances between 12.6 and 12.2. This base pair hel ps to anchor the D-loop to the T psi C loop.