Structural dynamic and thermodynamic analysis of calcineurin B subunit induced by calcium/magnesium binding
2013
Li, Feng | Yu, Ting | Yu, Shaoning
The structural dynamics and thermodynamics of the interaction of Ca²⁺/Mg²⁺ 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 Ca²⁺ binding involves significant conformational changes with a marked increase in the α-helix content, whereas Mg²⁺ 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 Ca²⁺-loaded CNB (CNB-Ca²⁺) is more stable and has more hydrophobic areas than that of Ca²⁺-free CNB (apo-CNB) or Mg²⁺-loaded CNB (CNB-Mg²⁺). The thermodynamic characterization suggests that there is no competition between Ca²⁺ and Mg²⁺ in their binding to the main CNB Ca²⁺ binding sites. Mg²⁺ is more likely to bind the auxiliary cation-binding sites present on CNB.
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