Calbindin (CALB1) (rec.)

Calcium binding proteins (CBPs) regulate intracellular levels of calcium (Ca2+) ions. CBPs are involved in numerous functions, such as cell signaling, calcium uptake and transport, and cell motility. Calretinin (CR), calbindin D-28k (CB) and parvalbumin (PV) belong to the large family of EF-hand calcium-binding proteins. The EF-hand is an amino acid sequence with a characteristic three-dimensional helix-loop-helix structure with high affinity for Ca2+. Calbindin D28k (calbindin) is a hexa EF-hand protein of 261 residues with 59% sequence identity to calretinin. It is a single-domain protein and the six EF hands interact extensively with one another so that they form one large globular domain. Calbindin is found in the brain and central nervous system with a distinct distribution over certain neuronal subtypes. Neuroprotective effects of calbindin has been reported in ischemic and glutamate toxicity models, primarily due to its ability to chelate calcium. Mice lacking calbindin have been shown to suffer from impaired motor coordination due to altered neuronal Ca2+-homeostasis. Notably, calbindin is found in high concentration in the kidney and in pancreatic beta-cells, where it has been shown to protect against apoptosis. In osteoblasts, anti-apoptic activity of calbindin through the binding to caspase-3 has also been reported. Calbindin protects against apoptotic and necrotic cell death, suggesting its ability to buffer calcium. Calbindin has been reported to binds Zn2+, revealing negative allosteric effect between the Zn2+- and Ca2+-binding events.