Mg super(2+) and a Key Lysine Modulate Exchange Activity of Eukaryotic Translation Elongation Factor 1B alpha

• Published in: The Journal of biological chemistry Vol. 281; no. 28; pp. 19457 - 19468
• Main Authors: Pittman, Yvette R, Valente, Louis, Jeppesen, Mads Gravers, Andersen, Gregers Rom, Patel, Smita, Kinzy, Terri Goss
• Format: Journal Article
• Language: English
• Published: 01.07.2006
• ISSN: 0021-9258; 1083-351X

To sustain efficient translation, eukaryotic elongation factor B alpha (eEF1B alpha ) 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 eEF1B alpha . The eEF1B alpha -stimulated reaction was inhibited by Mg super(2+) with a K sub( one half ) of 3.8 mM. Previous structural studies predicted the Lys-205 residue of eEF1B alpha plays an important role in promoting nucleotide exchange by disrupting the Mg super(2+) binding site. Co-crystal structures of the lethal K205A mutant in the catalytic C terminus of eEF1B alpha 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 Mg super(2+).A K205R eEF1B alpha mutant on the other hand was functional in vivo and showed nearly wild-type nucleotide dissociation rates but almost no sensitivity to Mg super(2+). These results indicate the significant role of Mg super(2+) in the nucleotide exchange reaction by eEF1B alpha and establish the catalytic function of Lys-205 in displacing Mg super(2+) from its binding site.