Proton nuclear magnetic resonance study on the roles of histidine residues in the binding of polypeptide chain elongation factor Tu from Thermus thermophilus with aminoacyl transfer ribonucleic acid and guanine nucleotides

Proton nuclear magnetic resonance (1H NMR) spectra were measured of the polypeptide chain elongation factor Tu (EF-Tu) from an extreme thermophile, Thermus thermophilus HB8 [Nakano, A., Miyazawa, T., Nakamura, S., & Kaziro, Y. (1979) Arch. Biochem. Biophys. 196, 233-238], in order to elucidate the environment around functionally important histidine residues. In the present study, the behavior of five histidine C2 proton signals was studied in more detail. A hydrogen-deuterium exchange experiment was carried out on the histidine C2 protons of free EF-Tu, and the previous assignments of C2 proton signals were revised in part. An analysis of the 1H NMR spectra of EF-Tu photooxidized under various conditions indicates that a histidine residue is located in the aminoacyl-tRNA binding site and is probably essential for the binding with aminoacyl-tRNA. A solvent-accessible histidine residue is found to lie near the aminoacyl-tRNA binding site. Furthermore, the effect of paramagnetic hexacyanochromate(III) ion on the 1H NMR spectra of free EF-Tu suggests that another histidine residue lies near the guanine nucleotide binding site.