?
 
C-terminal regulatory domain of Calcineurin B-Like (CBL)-interacting protein kinases CIPKs are serine/threonine protein kinases (STKs), catalyzing the transfer of the gamma-phosphoryl group from ATP to S/T residues on protein substrates. They comprise a unique family in higher plants of proteins that interact with the calcineurin B-like (CBL) calcium sensors to form a signaling network that decode specific calcium signals triggered by a variety of environmental stimuli including salinity, drought, cold, light, and mechanical perturbation, among others. The specificity of the response relies on differences in expression and localization of both CBLs and CIPKs, as well as on the interaction specificity of CBL-CIPK combinations. There are 25, 30, and 43 CIPK genes identified in the Arabidopsis thaliana, Oryza sativa, and Zea mays genomes, respectively. The founding member of the CIPK family is Arabidopsis thaliana CIPK24, also called SOS2 (Salt Overlay Sensitive 2). CIPKs contain an N-terminal catalytic kinase domain and a C-terminal regulatory domain that contains the FISL (also called NAF for Asn-Ala-Phe) and PPI-binding motifs, which are involved in the interaction with CBLs and PP2C-type protein phosphatases, respectively. Studies using SOS2, SOS3, and ABI2 phosphatase show that the binding of CBL and PP2C-type protein phosphatase to CIPK is mutually exclusive. The binding of CBL to CIPK is inhibitory to kinase activity. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",