Aminoacyl transfer ribonucleic acid binding site of the bacterial elongation factor Tu

Hydrolysis protection experiments were used for a quantitative determination of the binding of several aminoacyl-tRNAs to the Escherichia coli elongation factor Tu. The observed differences could not be rationalized in terms of structural properties of the tRNAs. The experimental results support, however, a model according to which the differences in the affinity of naturally occurring aminoacyl-tRNAs are determined mainly by the nature of the amino acid esterified to the tRNA. Aminoacyl-tRNAs with polar amino acid side chains are bound less strongly than those with apolar ones. This model is substantiated by results obtained with misacylated and modified aminoacyl-tRNAs. Furthermore, it could be shown that the aminoacyl group of the aminoacyl-tRNA must be in the L configuration; EF-Tu in this way prevents blocking of the ribosomal A site or even incorporation of D-amino acids into protein. The data have been used for a schematic description of the structure of a part of the aminoacyl-tRNA binding site of the bacterial elongation factor Tu.