CIPK serine-threonine protein kinases interact with CBL proteins. Binding of a CBL protein to the regulatory NAF domain of CIPK protein lead to the activation of the kinase in a calcium-dependent manner. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with CBL1 (PubMed:10590166, PubMed:11115898, PubMed:14730064). Interacts with CBL2 (PubMed:11230129). Interacts with CBL3 (PubMed:11115898, PubMed:11230129). Interacts with CBL9 (PubMed:14730064). Interacts with ECT1 and ECT2 (PubMed:16113215). Ubiquitous. The activation loop within the kinase domain is the target of phosphorylation/activation by upstream protein kinases. The PPI motif mediates the interaction with the ABI (abscisic acid-insensitive) phosphatases (By similarity). Autophosphorylated. May be due to intron retention. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. SNF1 subfamily.