NMR studies of ion binding to Escherichia coli tRNAPhe

Abstract

The effects of Mg, spermine and temperature on the conformation of E. coli tRNAPhe were examined by proton and P NMR spectroscopy. In the low-field proton NMR spectra 2 slowly interconverting conformations of this tRNA were characterized at low Mg ion concentrations. The relative proportion of the conformers is ion dependent but not ion specific. Mg affects protons in all the stems of tRNA while spermine effects are localized near the s4U-8.sbd.A-14 and G-15.sbd.C-48 tertiary bonds. The effects seen in the proton NMR spectra are compared and correlated with those observed in the P spectra to given assignments of dome of the resolved signals from the phosphate groups. The P spectra are compared with those of yeast tRNAPhe, and the ion effects are discussed with reference to the Mg and spermine sites found in the crystal structures of yeast tRNAPhe.