The Eukaryotic Translation Elongation Factor 1Bγ Has a Non-guanine Nucleotide Exchange Factor Role in Protein Metabolism

The turnover of damaged proteins is critical to cell survival during stressful conditions such as heat shock or oxidative stress. The accumulation of misfolded proteins in the endoplasmic reticulum (ER) is toxic to cells. Therefore these proteins must be efficiently exported from the ER and degraded by the proteasome or the vacuole. Previously it was shown that the loss of eukaryotic elongation factor 1B gamma (eEF1B gamma) from the yeast Saccharomyces cerevisiae results in resistance to oxidative stress. Strains lacking eEF1B gamma show severe defects in protein turnover during conditions of oxidative stress. Furthermore, these strains accumulate a greater amount of oxidized proteins, which correlates with changes in heat shock chaperones. These strains show severe defects in vacuole morphology and defects related to the maturation of carboxypeptidase Y that is not dependent on the catalytic subunit of the eEF1B complex as a guanine nucleotide exchange factor. Finally, eEF1B gamma co-immunoprecipitates with an essential component of ER-Golgi transport vesicles. Taken together, these results support a broader protein metabolism role for eEF1B gamma.