CIB1(also designated calcium and integrin binding 1 or calmyrin),with 191-amino acid protein(about 21kDa), belongs to the calcium-binding protein family.CIB1 is known to interact with DNA-dependent protein kinase and may play a role in kinase-phosphatase regulation of DNA end joining.CIB1 is an EF-hand-containing protein that binds multiple effector proteins, including the platelet alpha(IIb)beta(3) integrin and several serine/threonine kinases and potentially modulates their function.CIB1 regulates platelet aggregation in hemostasis through a specific interaction with the alpha(IIb) cytoplasmic domain of platelet integrin alpha(IIb)beta(3). CIB1 is also ubiquitously expressed activating and inhibiting protein ligand of the InsP3R.