Physical studies of denatured tRNA2Glu from Escherichia coli.

Abstract
The 270 MHz NMR spectrum and relaxation kinetic behavior of .**GRAPHIC**. (E. coli) was examined in the absence of Mg2+, a condition which produces an inactive form of this tRNA. The denatured form has about 5 fewer proton resonances in the region from -12 to -15 ppm. Relaxation kinetic measurements reveal that the denatured conformer contains 3 separately melting helices. The results support a model in which the tertiary structure and dihydrouridine helix characteristic of the native form are unfolded in the denatured state, and are replaced by an altered tertiary structure. The acceptor stem, anticodon and T.PSI.C helices are intact in this model for the denatured conformation. The optical changes that accompany melting of the denatured teritary structure are faster than 10 .mu.s.