Crystal structures of nucleotide exchange intermediates in the eEF1A-eEF1Balpha complex

In the elongation cycle of protein biosynthesis, the nucleotide exchange fa ctor eEF1B alpha catalyzes the exchange of GDP bound to the G-protein, eEF1 A, for GTP. To obtain more information about the recently solved eEF1A-eF1B alpha structure, we determined the structures of the eEF1A-eEF1B alpha -GD P-Mg2+, eEIF1A-eEF1B alpha -GDP and eEF1A-eEF1B alpha -GDPNP complexes at 3 .0, 2.4 and 2.05 Angstrom resolution, respectively. Minor changes, specific ally around the nucleotide binding site, in eEF1A and eEF1Ba are consistent with in vivo data. The base, sugar and alpha -phosphate bind as in other k nown nucleotide G-protein complexes, whereas the beta- and gamma -phosphate s are disordered. A mutation of Lys 205 in eEF1B alpha that inserts into th e Mg2+ binding site of eEF1A is lethal. This together with the structures e mphasizes the essential role of Mg2+ in nucleotide exchange in the eEF1A-eE F1B alpha complex.