Calponin is a calcium binding protein that is known for binding to a number of things, including actin, myosin, and tropomyosin. In smooth muscle, it also inhibits the ATPase activity of myosin.
Calponin typically consists of α-helices and hydrogen bond turns. A binding protein composed of three domains, these domains are Click-23, regulatory domain (referred to as RD), and Calponin Homology (referred to as CH). The CH domain calponin will bind to α-actin and filamin, and when it’s in conjunction with the RD domain, will bind to actin. Calmodulin can sometimes bind weakly to the CH domain if it is activated by calcium, and may also inhibit calponin binding with α-actin. Within the body, it is responsible for a number of things, including binding actin proteins, as well as phospholipids. It’s also in charge of regulating the actin/myosin interaction.
If the Calponin is phosphorylated by a protein kinase, then the Calponin’s inhibition of the smooth muscle ATPase will be released. It was first discovered in 1986, when Calponin was isolated from both chicken gizzard and bovine aorta and was found to be stable under heat. It is found in humans and other mammals. It is represented in both smooth muscle and non-muscle cell, as well as three different forms that have been identified in the vertebrae.