Inactivation of Tu Factor-Guanosine Triphosphate Recognition and Ribosome-binding Ability by Terminal Oxidation-Reduction of Yeast Phenylalanine Transfer Ribonucleic Acid

Cleavage of the 2',3'-carbon-carbon bond of the 3'-terminal adenosine residue of yeast tRNAphe and Escherichia coli tRNAtyr was effected by oxidation with sodium periodate at pH 6 followed by reduction of the dialdehyde to the diol by sodium borohydride at pH 8. Both of these tRNA species could still be acylated by their respective amino acids and cognate synthetases. tRNAphe retained 82% of its acceptance capacity and tRNA tyr retained 50% activity. On the other hand, oxidized-reduced Phe-tRNA could no longer form a ternary complex with E. coli Tu factor and GTP, demonstrating that intactness of this end of the tRNA molecule is important in this recognition reaction. This modification also blocked T-factor-dependent Phe-tRNA binding to the A site on the ribosome, and severely inhibited nonenzymatic binding at the P site at 4 to 6 mm Mg++ relative to control Phe-tRNA's although most of the inhibitory effect at this site could be abolished by raising the Mg++ concentration to 15 to 20 mm.