Substrate Properties of Yeast tRNAPhe Oxidized and Reduced at the 3′‐Terminal Ribose

Abstract

Native yeast tRNAPhe and this tRNAPhe with the 3′‐terminal AMP removed were oxidized by NaIO4 and subsequently reduced by NaBH4. The following investigations were undertaken with these substrates: aminoacylation in borate buffer and measurement of the life‐time of the aminoacylated oxidized an reduced tRNA, hydrolysis with snake‐venom phosphodiesterase and pyrophosphorolysis with tRNA nucleotidyl transferase.Whereas the oxidized and reduced yeast tRNAPhe is a good substrate for the enzymes investigated, the corresponding tRNAPhe with the 3′‐terminal AMP removed is a very poor, if any, substrate in these reactions. From the data obtained and from proton‐magnetic‐resonance investigations with oxidized and reduced AMP and ATP it is concluded that the removal of the C2′—C3′ bond and introduction of two hydrogen atoms instead distorts the original ribose conformation at the 3′‐terminus. Under the assumption that this distortion is different for C75 and A76 the difference in reactivity between the two oxidized and reduced tRNAs can be explained.