Structural Studies on Calcium/calmodulin-dependent Activation of Eukaryotic Elongation Factor 2 Kinase
Eukaryotic elongation factor 2 kinase (eEF-2K) is a key modulator of the rate of protein synthesis. Activated by calcium-loaded calmodulin (Ca2+-CaM), eEF-2K phosphorylates its only known physiological substrate, eEF-2, on a specific threonine residue (Thr-56). Phosphorylated eEF-2 has reduced affinity for the ribosome, and results in a significant decrease in the rate of translation elongation. Modulation of the rate of translation elongation plays a crucial role in proteostasis – adequate regulation of protein synthesis, protein folding, and protein degradation that greatly influences cellular growth and survival. Binding of Ca2+-CaM triggers activation of eEF-2K and remains intact to facilitate the substrate phosphorylation, acting as a cofactor of the enzyme. Despite its importance, how the binding of Ca2+-CaM leads to activation remains poorly understood. We employed various biophysical tools, such as nuclear magnetic resonance (NMR) spectroscopy and isothermal titration calorimetry (ITC), coupled with mutational strategies to characterize structural and thermodynamic nature of the binding of Ca2+-CaM onto eEF-2K. Our data clarify the roles of Ca2+ and each lobe of CaM that provide mechanistic insight into the structural regulation of eEF-2K mediated by the binding of Ca2+-CaM.
Biochemistry, Biophysics, Structural Biology, calmodulin, eEF-2K, NMR, ITC
City University of New York - Graduate Center
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The Graduate School and University Center of The City University of New York