Calponin is a basic 34-kD protein first isolated from chicken gizzard and bovine aorta. It is specifically expressed in smooth muscle and binds calmodulin, actin, and tropomyosin. It is able to inhibit the ATPase activity of myosin and is though to play a role in smooth muscle contraction. Calponin is a smooth muscle specific, actin-, tropomyosin- and calmodulin-binding protein thought to be involved in some way in the regulation or modulation of contraction.
