title: Structural dynamic and thermodynamic analysis of calcineurin B subunit induced by calcium/magnesium binding.
abstract: The structural dynamics and thermodynamics of the interaction of Ca(2+)/Mg(2+) with the calcineurin B subunit (CNB) were monitored by Fourier transform infrared spectroscopy (FT-IR) and isothermal titration calorimetry (ITC). The results suggest that CNB activation by Ca(2+) binding involves significant conformational changes with a marked increase in the α-helix content, whereas Mg(2+) binds to CNB without inducing changes in secondary structure. The results of hydrogendeuterium (HD) exchange and GdnHCl-induced unfolding show that the overall conformation of Ca(2+)-loaded CNB (CNB-Ca(2+)) is more stable and has more hydrophobic areas than that of Ca(2+)-free CNB (apo-CNB) or Mg(2+)-loaded CNB (CNB-Mg(2+)). The thermodynamic characterization suggests that there is no competition between Ca(2+) and Mg(2+) in their binding to the main CNB Ca(2+) binding sites. Mg(2+) is more likely to bind the auxiliary cation-binding sites present on CNB.
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Ting
authors.initials: T
authors.lastname: Yu
authors.forename: Shaoning
authors.initials: S
authors.lastname: Yu
mesh_terms: D001665:Binding Sites; D019703:Calcineurin / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D008274:Magnesium / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D013816:Thermodynamics
chemical_list: D019703:Calcineurin; D008274:Magnesium; D002118:Calcium
keywords: CD; CN; CNA; CNB; CaBPs; Calcineurin B subunit; FKBP12; FT-IR spectroscopy; Fourier transform infrared spectroscopy; GdnHCl; HD exchange; IPTG; ITC; NFAT; Structural dynamics; Thermodynamics; calcineurin; calcineurin A; calcineurin B subunit; calcium binding proteins; circular dichroism; guanidine hydrochloride; hydrogendeuterium exchange; isopropyl thiogalactopyranoside; isothermal titration calorimetry; nuclear factor of activated T cells; the FK506-binding protein