Effect of uridine dethiolation in the anticodon triplet of trna(Glu) on its association with trna(phe)

The effect of U(34) dethiolation on the anticodon-anticodon association between E.coli tRNA(Glu) and yeast tRNA(Phe) has been studied by jhe temperature jump relaxation technique. An important destabilization upon replacement of the thioketo group of s2U(34) by a keto group, was revealed by a lowering of melting temperature of about 20° C. The measured kinetic parameters indicated that this destabilization effect was originated in an increase of dissociation and a decrease of association rate constants by a factor of 4 to 5. Modifications in both stacking interactions and flexibility in the anticodon loop would be responsible for this effect.