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

Abstract

Hydrolysis protection experiments were used for a quantitative determination of the binding of several aminoacyl-tRNA to the Escherichia coli elongation factor Tu. The observed differences could not be rationalized in terms of structural properties of the tRNA. The experimental results support a model according to which the differences in the affinity of naturally occurring aminoacyl-tRNA are determined mainly by the nature of the amino acid esterified to the tRNA. Aminoacyl-tRNA 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-tRNA. The aminoacyl group of the aminoacyl-tRNA must be in the L configuration; EF-Tu in this way prevents blocking of the ribosomal A [aminoacyl] site or even incorporation of D-amino acids into protein. The data were used for a schematic description of the structure of a part of the aminoacyl-tRNA binding site of the bacterial elongation factor Tu.