Mg2+ and a Key Lysine Modulate Exchange Activity of Eukaryotic Translation Elongation Factor 1Bα
Journal of Biological Chemistry
To sustain efficient translation, eukaryotic elongation factor Bα (eEF1Bα) functions as the guanine nucleotide exchange factor for eEF1A. Stopped-flow kinetics using 2′-(or 3′)-O-N-methylanthraniloyl (mant)-GDP showed spontaneous release of nucleotide from eEF1A is extremely slow and accelerated 700-fold by eEF1Bα. The eEF1Bα-stimulated reaction was inhibited by Mg2+ with a K½ of 3.8 mm. Previous structural studies predicted the Lys-205 residue of eEF1Bα plays an important role in promoting nucleotide exchange by disrupting the Mg2+ binding site. Co-crystal structures of the lethal K205A mutant in the catalytic C terminus of eEF1Bα with eEF1A and eEF1A·GDP established that the lethality was not due to a structural defect. Instead, the K205A mutant drastically reduced the nucleotide exchange activity even at very low concentrations of Mg2+.A K205R eEF1Bα mutant on the other hand was functional in vivo and showed nearly wild-type nucleotide dissociation rates but almost no sensitivity to Mg2+. These results indicate the significant role of Mg2+ in the nucleotide exchange reaction by eEF1Bα and establish the catalytic function of Lys-205 in displacing Mg2+ from its binding site.
Pittman, Yvette R.; Valente, Louis; Jeppesen, Mads Gravers; Andersen, Gregers Rom; Patel, Smita; and Kinzy, Terri Goss, "Mg2+ and a Key Lysine Modulate Exchange Activity of Eukaryotic Translation Elongation Factor 1Bα" (2006). Faculty Publications – Biological Sciences. 94.