Crystal Structures of Nucleotide Exchange Intermediates in the eEF1A–eEF1Bα Complex

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Nature Structural & Molecular Biology

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In the elongation cycle of protein biosynthesis, the nucleotide exchange factor eEF1Bα catalyzes the exchange of GDP bound to the G-protein, eEF1A, for GTP. To obtain more information about the recently solved eEF1A–eEF1Bα structure, we determined the structures of the eEF1A–eEF1Bα–GDP–Mg2+, eEF1A–eEF1Bα–GDP and eEF1A–eEF1Bα–GDPNP complexes at 3.0, 2.4 and 2.05 Å resolution, respectively. Minor changes, specifically around the nucleotide binding site, in eEF1A and eEF1Bα are consistent with in vivo data. The base, sugar and α-phosphate bind as in other known nucleotide G-protein complexes, whereas the β- and γ-phosphates are disordered. A mutation of Lys 205 in eEF1Bα that inserts into the Mg2+ binding site of eEF1A is lethal. This together with the structures emphasizes the essential role of Mg2+ in nucleotide exchange in the eEF1A–eEF1Bα complex.