title: Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation.
abstract: Calcineurin (CN) is a Ca(2+)/calmodulin (CaM) activated serine/threonine phosphatase, and its regulatory region (CNRR) plays a critical role in the coupling of Ca(2+) signals to cellular responses. Ca(2+)/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 Ca(2+)/CaM using isothermal titration calorimetry (ITC). The structural change in CNRR381-521 induced by Ca(2+)/CaM binding was also investigated by Fourier transform infrared spectroscopy (FT-IR). The results indicate that Ca(2+)/CaM binding to CNRR381-521 is an exothermic reaction with a dissociation constant of 2.0×10(-6) M. Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation.
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433, China.
authors.forename: Cuiping
authors.initials: C
authors.lastname: Fu
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433, China.
authors.forename: Junting
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Shanghai Pinghe Bilingual School, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Clinical Pharmacy, Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai 200080, China. Electronic address: Xuhongbing99@163.com.
authors.forename: Hongbing
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433, China. Electronic address: yushaoning@fudan.edu.cn.
authors.forename: Shaoning
authors.initials: S
authors.lastname: Yu
mesh_terms: D001665:Binding Sites; D019703:Calcineurin / Q000737:chemistry* / Q000235:genetics; D002118:Calcium / Q000737:chemistry*; D002147:Calmodulin / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D002147:Calmodulin; D011994:Recombinant Proteins; D019703:Calcineurin; D002118:Calcium
keywords: Calcineurin; Calcineurin regulatory region; Calmodulin; FT-IR spectroscopy; ITC