Calcineurin (CaN), also called protein phosphatase 2B (PP2B), is a calcium/Calmodulin (CaM)-dependent serine/threonine protein phosphatase. It exists as a heterodimer consisting of CaM-binding catalytic subunit CaN A chain and a Ca+2 binding regulatory CaN B chain. At low calcium concentrations, CaN exists in an inactive state, where the autoinhibitory domain (AID) binds to the active-site cleft. Upon an increase in calcium concentration CaM binds to Ca+2 ions and gets activated. Active CaM binds to CaN regulatory domain (RD) and this causes release of the AID and activation of the phosphatase (Rumi-Masante et al. 2012). Binding of calcium to CaN B regulatory chain also causes a conformational change of the RD of CaN A chain (Yang & Klee 2000).