Acts as a calcium sensor involved in the regulatory pathway for the control of intracellular Na(+) and K(+) homeostasis and salt tolerance. Binding of a CBL protein to the regulatory NAF domain of a CIPK serine-threonine protein kinase lead to the activation of the kinase in a calcium-dependent manner. Operates in synergy with CIPK24/SOS2 to activate the plasma membrane Na(+)/H(+) antiporter SOS1. Involved in salt stress responses by mediating calcium-dependent microfilament reorganization. The CBL4/CIPK6 complex mediates translocation of AKT2 from the endoplasmic reticulum to the plasma membrane. Both myristoylation and S-acylation are required for AKT2 activation. Binds 4 Ca(2+) ions per subunit. Interacts with CIPK24/SOS2, CIPK6/SIP3, CIPK10/SIP1, CIPK11/SIP4 and CIPK15/SIP2. Homodimer, mediated by calcium-binding. Binds to ABCG36 (PubMed:26315018). The cell membrane localization is S-acylation dependent. The calcium-binding domain (165-176) of the EF-hand 4 can also interacts with a manganese ion. The N-terminal 18 amino acids are sufficient for the cell membrane targeting of a heterologous protein. Both N-myristoylation and calcium-mediated conformational changes are essential for its function. S-acylated at Cys-3. Phosphorylated by CIPK6 and CIPK24. Delayed development and flowering. Belongs to the calcineurin regulatory subunit family.