ISOMERIC SPECIFICITY OF AMINOACYLATION OF WHEAT-GERM TRANSFER RIBONUCLEIC-ACID AND THE SPECIFICITY OF INTERACTION OF ELONGATION-FACTOR TU WITH AMINOACYL TRANSFER RIBONUCLEIC-ACID

The initial site of aminoacylation of wheat germ transfer RNA has been determined for all 20 amino acids. The method employed involves the use of an analogue of tRNA (Fraser, T. H., and Rich, A. (1973) Proc. Natl. Acad. Sci. U. S. A. 70, 2671-2675; (1975) Proc. Natl. Acad. Sci. U. S. A. 72, 3044-3048) in which either the 2'-or 3'-hydroxyl group at the 3' end of the molecule is replaced with an amino group. By comparison of these results with earlier findings for Escherichia coli tRNA (Fraser, T. H., & Rich, A. (1975) Proc. Natl. Acad. Sci. U. S. A. 72, 3044-3048) it appears that the specificity of this reaction has been maintained during the evolutionary process. However, it has been found that some E. coli aminoacyl-tRNA synthetases differ from those in wheat germ in their ability to catalyze amide bond formation. We have also examined the interaction of both the 2'-and 3'-amino isomers of E. coli tRNA with elongation factor Tu and GTP. Both of these positional isomers are capable of participating in ternary complex formation, even though such a complex appears to be weaker than that formed with normal tRNA. In light of the finding that EF-Tu can accept either the 2'-or 3'-amino-tRNA analogue for complex formation, it seems that the positional specificity of the initial aminoacylation plays no role in determining the specificity of subsequent steps in ribosomal protein synthesis. © 1979, American Chemical Society. All rights reserved.