This is a calcium-activated, phospholipid-dependent, serine- and threonine-specific enzyme. This isozyme is a negative regulator of the visual transduction cascade and has been shown to be required for photoreceptor cell inactivation and light adaptation. Negative regulation is dependent on interaction with scaffolding protein inaD. Acts in a hh-signaling pathway which regulates the Duox-dependent gut immune response to bacterial uracil; required for the activation of Cad99C and consequently Cad99C-dependent endosome formation, which is essential for the Duox-dependent production of reactive oxygen species (ROS) in response to intestinal bacterial infection (PubMed:25639794). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Binds 3 Ca(2+) ions per C2 domain. Exclusively expressed in photoreceptor cells. Expression primarily in adults. Up-regulated in the midgut epithelium in response to bacterial uracil. Tetrapeptide ligand at C-terminus is tethered to inaD by interaction with the second PDZ domain. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. PKC subfamily.