Histidine 66 in Escherichia coli elongation factor Tu selectively stabilizes aminoacyl-tRNAs

Abstract

The universally conserved His-66 of elongation factor Tu (EFTu) stacks on the side chain of the esterified Phe of Phe-tRNA Phe. The affinities of eight aminoacyl-tRNAs were differentially destabilized by the introduction of the H66A mutation into Escherichia coli EF-Tu, whereas Ala-tRNA Ala and Gly-tRNA Gly were unaffected. The H66F and H66W proteins each show a different pattern of binding of 10 different aminoacyltRNAs, clearly showing that this position is critical in establishing the specificity of EF-Tu for different esterified amino acids. However, the H66A mutation does not greatly affect the ability of the ternary complex to bind ribosomes, hydrolyze GTP, or form dipeptide, suggesting that this residue does not directly participate in ribosomal decoding. Selective mutation of His-66 may improve the ability of certain unnatural amino acids to be incorporated by the ribosome. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.