Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation

• Published in: International journal of biological macromolecules Vol. 79; pp. 235 - 239
• Main Authors: Fu, Cuiping, Zhang, Junting, Zheng, Ye, Xu, Hongbing, Yu, Shaoning
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2015
• Subjects: Binding Sites; Calcineurin; Calcineurin - chemistry; Calcineurin - genetics; Calcineurin regulatory region; Calcium - chemistry; Calmodulin; Calmodulin - chemistry; Calmodulin - genetics; Cloning, Molecular; Escherichia coli - genetics; Escherichia coli - metabolism; FT-IR spectroscopy; Gene Expression; Humans; ITC; Kinetics; Models, Molecular; Protein Binding; Protein Stability; Protein Structure, Secondary; Protein Structure, Tertiary; Recombinant Proteins; Spectroscopy, Fourier Transform Infrared; Thermodynamics; FT-IR spectroscopy; Calcineurin; ITC; Calcineurin regulatory region; CN; CaM; Calmodulin; EGTA
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2015.04.069

Calcineurin (CN) is a Ca2+/calmodulin (CaM) activated serine/threonine phosphatase, and its regulatory region (CNRR) plays a critical role in the coupling of Ca2+ signals to cellular responses. Ca2+/CaM binds to the CNRR, resulting in a conformational change that removes an autoinhibitory domain (CN467–486) from the active site of the phosphatase and activates the enzyme. However, almost the entire regulatory region (CN374–521) is not visible in the electron density maps of reported structures. In this study, we produced separate CN fragments corresponding to the CNRR (CNRR381–521, CN residues 381–521) and determined the binding affinity of CNRR381–521 for Ca2+/CaM using isothermal titration calorimetry (ITC). The structural change in CNRR381–521 induced by Ca2+/CaM binding was also investigated by Fourier transform infrared spectroscopy (FT-IR). The results indicate that Ca2+/CaM binding to CNRR381–521 is an exothermic reaction with a dissociation constant of 2.0×10−6M. Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation.