– Hippocalcin-Like Protein 1 (HPCAL1) is a neuron-specific calcium-binding member of the recoverin family which found in the retina and brain. HPCAL1 contains four EF-hand domains and it is highly similar to human hippocalcin protein. HPCAL1 is involved in the calcium-dependent regulation of rhodopsin phosphorylation. In addition, it may be of relevance for neuronal signalling in the central nervous system.