Calbindin

Calbindin, also known as calbindin 1 or calbindin-D28k is a member of the large superfamily of cytoplasmic Ca2+ binding proteins. Calbindin-1 belongs to the subclass of these containing the "EF hand" Ca2+ binding motif originally characterized in parvalbumin. Calbindin is expressed in mammalian brain, intestine, kidney and pancreas. In the brain it is localized in certain classes of neurons, and antibodies to it are useful for identifying specific neuronal cell types. It is particularly concentrated in the dendrites and perikarya of cerebellar Purkinje cells, but is also found in many GABAergic interneurons in the cortex.

The function of calbindin-1 appears to be primarily buffering the Ca²⁺ level in cells. The affinity of calbindin for Ca²⁺ is low at the typical resting cytoplasmic Ca²⁺ level of around 100 nM, and the protein only binds Ca²⁺ significantly when levels increase greatly. Accordingly, it is widely thought that the primary function of this protein is to act as a Ca²⁺ buffer. Buffering Ca²⁺ is important, as uncontrolled increases in the level of this cation can lead to both apoptosis due to Ca²⁺stimulated release of proteins from mitochondria and necrosis due to the activation of Ca²⁺dependent proteases.