title: The salt bridge of calcineurin is important for transferring the effect of CNB binding to CNA.
abstract: Calcineurin (CN) is a heterodimer consisting of a catalytic subunit (CNA) and a regulatory subunit (CNB). The crystal structure shows that three residues or regions of CNA are mainly responsible for the interaction with CNB: the CNB binding helix (BBH), the N-terminus, and Glu53 that forms a salt bridge with Lys134 of CNB. In this report, we try to find the role that the salt bridge plays in the interaction between CNA and CNB. We found that mutation of Glu53 greatly reduced its responsiveness to CNB in the phosphatase assay and also that mutation of Lys134 of CNB affected its ability to activate the phosphatase activity of CNA. Structural analysis showed that disruption of the salt bridge affected the compact association of CNA and CNB. Thus, the salt bridge appears to help to stabilize CN and transfer the effects of CNB binding to CNA to activate its phosphatase activity.
authors.affiliation: Department of Biochemistry and Molecular Biology, Beijing Normal University, Beijing Key Laboratory, Beijing 100875, PR China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hou
authors.forename: Xiang
authors.initials: X
authors.lastname: Yi
authors.forename: Guohua
authors.initials: G
authors.lastname: Jiang
authors.forename: Qun
authors.initials: Q
authors.lastname: Wei
mesh_terms: D001483:Base Sequence; D019703:Calcineurin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D013056:Spectrophotometry, Ultraviolet
chemical_list: D017931:DNA Primers; D019703:Calcineurin