[A study of tRNA(adenine-1-)-methyltransferase from Thermus thermophilus HB8 with tRNA using enzymatic and spectral methods].

The contact sites of yeast tRNA1Val with tRNA(adenine-1-)-methyltransferase (EC 2.1.1.36) were studied by comparing the partial digests of free and enzyme bound tRNA. The RNAases Sa, V1, S1 and A were used for this purpose. Phosphodiester bonds on the proximal end of the acceptor stem and adjacent D- and T psi-stems, forming a continuous area, are protected by the methylase from the action of RNAases. On the contrary an enhancement of phosphodiester bond splitting of the D- and T psi-loops and of the anticodon stem is observed in the presence of methylase, which is interpreted as tertiary structure relaxation of tRNA owing to complex formation. The isotherm of ethidium bromide adsorption on free and methylase bound tRNA has shown that in enzyme shields approximately 50% of tRNA double stranded regions.