Structural basis for nucleotide exchange and competition with tRNA in the yeast elongation factor complex eEF1A:eEF1Bα

The crystal structure of a complex between the protein biosynthesis elongation factor eEF1A (formerly EF-1 alpha) and the catalytic C terminus of its exchange factor, eEF1B alpha (formerly EF-1 beta), was determined to 1.67 Angstrom resolution. One end of the nucleotide exchange factor is buried between the switch 1 and 2 regions of eEF1A and destroys the binding site for the Mg2+ ion associated with the nucleotide. The second end of eEF1B alpha interacts with domain 2 of eEF1A in the region hypothesized to be involved in the binding of the CCA-aminoacyl end of the tRNA. The competition between eEF1B alpha and aminoacylated tRNA may be a central element in channeling the reactants in eukaryotic protein synthesis. The recognition of eEF1A by eEF1B alpha is very different from that observed in the prokaryotic EF-Tu:EF-Ts complex. Recognition of the switch 2 region in nucleotide exchange is, however, common to the elongation factor complexes and those of Ras:Sos and Arf1:Sec7.