Purkinje cell protein 4 is a protein that in humans is encoded by the PCP4 gene. Also known as PEP-19, PCP4 is a 7.6 kDa protein with an IQ-motif that binds to calmodulin (CaM). PCP4 is abundant in Purkinje cells of the cerebellum, and plays an important role in synaptic plasticity.