Mutational analysis reveals potential phosphorylation sites in eukaryotic elongation factor 1A that are important for its activity.

Previous studies have suggested that phosphorylation of translation elongation factor 1A (eEF1A) can alter its function, and large-scale phospho-proteomic analyses in Saccharomyces cerevisiae have identified 14 eEF1A residues phosphorylated under various conditions. Here, a series of eEF1A mutations at these proposed sites were created and the effects on eEF1A activity were analyzed. The eEF1A-S53D and eEF1A-T430D phosphomimetic mutant strains were inviable, while corresponding alanine mutants survived but displayed defects in growth and protein synthesis. The activity of an eEF1A-S289D mutant was significantly reduced in the absence of the guanine nucleotide exchange factor eEF1Bα and could be restored by an exchange-deficient form of the protein, suggesting that eEF1Bα promotes eEF1A activity by a mechanism other than nucleotide exchange. Our data show that several of the phosphorylation sites identified by high-throughput analysis are critical for eEF1A function.