Calcium-Buffering Proteins: Calbindin

The calbindins, calbindin-D 9k and calbindin-D 28k , belong to a family of high-affinity calcium-binding proteins characterized by the EF hand structural motif. Calbindin was the first identified target of vitamin D action. It is now known that the calbindins are not exclusively regulated by vitamin D. They are present in many different tissues, serve different functions, and are regulated by factors other than 1,25(OH) 2 D 3 . Calbindin-D 28k is highly conserved in evolution. Calbindin-D 9k, however, is present only in mammals. Evidence suggests that calbindin-D 28k is involved in protection against apoptotic cell death by buffering calcium and by inhibiting caspase-3. Additional functions of calbindin include maintenance of intracellular calcium homeostasis and modulation of calcium influx.