title: Calcium-induced changes in calmodulin structural dynamics and thermodynamics.
abstract: The thermodynamics of the interaction between Ca(2+) and calmodulin (CaM) was examined using isothermal titration calorimetry (ITC). The chemical denaturation of calmodulin was monitored spectroscopically to determine the stability of Ca(2+)-free (apo) and Ca(2+)-loaded (holo) CaMs. We explored the conformational and structural dynamics of CaM using amide hydrogen-deuterium (H-D) exchange coupled with Fourier transform infrared (FT-IR) spectroscopy. The results of H-D exchange and FT-IR suggest that CaM activation by Ca(2+) binding involves significant conformational changes. The results have also revealed that while the overall conformation of holo-CaM is more stable than that of the apo-CaM, some part of its α-helix structures, most likely the EF-hand domain region, has more solvent exposure, thus, has a faster H-D exchange rate than that of the apo-CaM. The ITC method provides a new strategy for obtaining site-specific Ca(2+) binding properties and a better estimation of the cooperativity and conformational change contributions of coupled EF-hand proteins.
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433 China.
authors.forename: Guangrong
authors.initials: G
authors.lastname: Wu
authors.forename: Zhengya
authors.initials: Z
authors.lastname: Gao
authors.forename: Aichun
authors.initials: A
authors.lastname: Dong
authors.forename: Shaoning
authors.initials: S
authors.lastname: Yu
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology*; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism*; D019791:Guanidine / Q000494:pharmacology; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D058767:Protein Unfolding / Q000187:drug effects; D013057:Spectrum Analysis; D013379:Substrate Specificity; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D002147:Calmodulin; D014867:Water; D019791:Guanidine; D002118:Calcium