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Nucleotide-free structure of a functional construct of eukaryotic elongation factor 2 kinase.Nucleotide-free structure of a functional construct of eukaryotic elongation factor 2 kinase.
Structural highlights
FunctionEF2K_HUMAN Threonine kinase that regulates protein synthesis by controlling the rate of peptide chain elongation. Upon activation by a variety of upstream kinases including AMPK or TRPM7, phosphorylates the elongation factor EEF2 at a single site, renders it unable to bind ribosomes and thus inactive. In turn, the rate of protein synthesis is reduced.[1] [2] Publication Abstract from PubMedProtein translation, one of the most energy-consumptive processes in a eukaryotic cell, requires robust regulation, especially under energy-deprived conditions. A critical component of this regulation is the suppression of translational elongation through reduced ribosome association of the GTPase eukaryotic elongation factor 2 (eEF-2) resulting from its specific phosphorylation by the calmodulin (CaM)-activated alpha-kinase eEF-2 kinase (eEF-2K). It has been suggested that the eEF-2K response to reduced cellular energy levels is indirect and mediated by the universal energy sensor AMP-activated protein kinase (AMPK) through direct stimulatory phosphorylation and/or downregulation of the eEF-2K-inhibitory nutrient-sensing mTOR pathway. Here, we provide structural, biochemical, and cell-biological evidence of a direct energy-sensing role of eEF-2K through its stimulation by ADP. A crystal structure of the nucleotide-bound complex between CaM and the functional core of eEF-2K phosphorylated at its primary stimulatory site (T348) reveals ADP bound at a unique pocket located on the face opposite that housing the kinase active site. Within this basic pocket (BP), created at the CaM/eEF-2K interface upon complex formation, ADP is stabilized through numerous interactions with both interacting partners. Biochemical analyses using wild-type eEF-2K and specific BP mutants indicate that ADP stabilizes CaM within the active complex, increasing the sensitivity of the kinase to CaM. Induction of energy stress through glycolysis inhibition results in significantly reduced enhancement of phosphorylated eEF-2 levels in cells expressing ADP-binding compromised BP mutants compared to cells expressing wild-type eEF-2K. These results suggest a direct energy-sensing role for eEF-2K through its cooperative interaction with CaM and ADP. ADP enhances the allosteric activation of eukaryotic elongation factor 2 kinase by calmodulin.,Piserchio A, Long KJ, Browning LS, Bohanon AL, Isiorho EA, Dalby KN, Ghose R Proc Natl Acad Sci U S A. 2023 Apr 25;120(17):e2300902120. doi: , 10.1073/pnas.2300902120. Epub 2023 Apr 17. PMID:37068230[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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