Eukaryotic elongation factor 2 kinase (eEF2k) phosphorylates and inactivates eEF2, thereby inhibiting peptide-chain elongation. eEF2k, which is Ca2+ and calmodulin dependent, can be activated by PKA in response to stress-induced elevation of cAMP levels. eEF2k expression is also modulated by a wide range of stimuli that promote cell growth and protein synthesis. Phosphorylation of eEF2k by p90RSK and p70 S6 kinase at Ser366 or by SAPK4/p38d at Ser359, inactivates eEF2k, which facilitates the dephosphorylation of eEF2, and thus promotes translation.
