Conformational dynamics of calmodulin in complex with the calmodulin-dependent kinase kinase alpha calmodulin-binding domain.
As the primary intracellular calcium sensor, calcium-saturated calmodulin (CaM) regulates numerous and diverse proteins. Several mechanisms, including tissue-specific expression, localization, and sequestration, work in concert to limit the total number of available targets of calmodulin within a cell. While the free energies of binding of calmodulin-binding domains of regulated proteins by CaM have been shown to be highly similar, they result from vastly different enthalpic and entropic contributions. Here, we report the backbone and side-chain methyl dynamics of calcium-activated calmodulin in complex with a peptide corresponding to the CaM-binding domain of calmodulin kinase kinase, along with the thermodynamic underpinnings of complex formation. The results show a considerable reduction in side-chain mobility throughout CaM upon binding the CaMKKalpha peptide, which is consistent with the enthalpically driven nature of the binding. Site-specific comparison to another kinase-derived peptide complex with similar thermodynamic values reveals significant differences in dynamics largely localized to the hydrophobic binding sites.
Marlow
Michael S
MS
Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059, USA.
Wand
A Joshua
AJ
D000818:Animals; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D002147:Calmodulin / Q000378:metabolism*; D002151:Calorimetry; D002645:Chickens; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013816:Thermodynamics
D002147:Calmodulin; D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase