Thermodynamic Analysis of Calcium and Magnesium Binding to Calmodulin
| Autor: | Jacques Haiech, Robert Gilli, A. A. Makarov, M.-C. Kilhoffer, Daniel Lafitte, Claudette Briand, C. Lopez |
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| Rok vydání: | 1998 |
| Předmět: |
Isothermal microcalorimetry
Binding Sites animal structures Calmodulin biology Protein Conformation Chemistry Enthalpy Allosteric regulation Calorimetry Biochemistry Ion binding Protein structure biology.protein Biophysics Thermodynamics Physical chemistry Calcium Magnesium Binding site Dialysis Entropy (order and disorder) |
| Zdroj: | Biochemistry. 37:5450-5456 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi972083a |
| Popis: | To elucidate some aspects still debated concerning the interaction of Ca2+ and Mg2+ with CaM, the thermodynamic binding parameters of Ca2+-CaM and Mg2+-CaM complexes were characterized by flow dialysis and isothermal microcalorimetry under different experimental conditions. In particular, the enthalpy and entropy changes associated with Ca2+ and Mg2+ binding to their sites were determined, allowing a better understanding of the mechanism underlying cation-CaM interactions. Ca2+-CaM interaction follows an enthalpy-entropy compensation relationship, suggesting that CaM explores a subspace of isoenergetical conformations which is modified by Ca2+ binding. This Ca2+-induced change in CaM dynamics is proposed to play a key role in CaM function, i.e. in its interaction with and/or activation of target proteins. Furthermore, data show that Mg2+ does not act as a direct competitor for Ca2+ binding on the four main Ca2+ binding sites, but rather as an allosteric effector. This implies that the four main Mg2+ binding sites are distinct from the EF-hand Ca2+ binding sites. Finally, Ca2+ is shown to interact with auxiliary binding sites on CaM. These weak affinity sites were thermodynamically characterized. The results presented here challenge the current accepted view of CaM ion binding. |
| Databáze: | OpenAIRE |
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