Calcium Binding Proteins typically belong to the same evolutionary family and often share an EF-hand calcium-binding domain that consists of a 12 residue loop flanked on both sides by a 12 residue alpha-helical domain; the calcium ion is coordinated with oxygen of Glu or Asp residues in a pentagonal bipyramidal configuration. Reversible binding of calcium with proteins often supports protein structure or induces an alteration of protein activity in enzymatic or cell signaling cascades. Calcium is essential for maintenance of a normal heartbeat and for normal cell functions. It also plays a role in blood coagulation and in many enzymatic processes. [ ]