EFFECTOR REGION OF THE TRANSLATION ELONGATION-FACTOR EF-TU GTP COMPLEX STABILIZES AN ORTHOESTER ACID INTERMEDIATE STRUCTURE OF AMINOACYL-TRANSFER-RNA IN A TERNARY COMPLEX

tRNA(Val) from Escherichia coli was aminoacylated with [1-C-13]valine and its complex with Thermus thermophilus elongation factor EF-Tu.GTP was analyzed by C-13 NMR spectroscopy. The results suggest that the aminoacyl residue of the valyl-tRNA in ternary complex with bacterial EF-Tu and GTP is not attached to tRNA by a regular ester bond to either a 2'- or 3' hydroxyl group; instead, an intermediate orthoester acid structure with covalent linkage to both vicinal hydroxyls of the terminal adenosine-76 is formed. Mutation of arginine-59 located in the effector region of EF-Tu, a conserved residue in protein elongation factors and the alpha subunits of heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), abolishes the stabilization of the orthoester acid structure of aminoacyl-tRNA.