Module 4: Figure calcineurin
Calcineurin (CaN) is a Ca2+/calmodulin-sensitive serine/threonine protein phosphatase.
Shown on the top is the catalytic calcineurin A (CaNA) subunit, which has the catalytic site, a calcineurin B-binding domain (CaNB-BD), a calmodulin (CaM)-binding domain (CaM-BD) and an autoinhibitory domain (AID) that inhibits the catalytic site in the inactive state. CaNB is an EF-hand Ca2+-binding protein that has a similar structure to CaM and is bound to the enzyme under resting conditions. The stimulatory action of Ca2+ is carried out by two Ca2+ sensors, CaNB and CaM, which act by removing the inhibitory effect of AID that occurs in two steps, as described in the text.