Calponin tonically inhibits the ATPase activity of myosin in smooth muscle.

Phosphorylation of calponin by a protein kinase, which is dependent upon calcium binding to calmodulin, releases the calponin's inhibition of the smooth muscle ATPase.

Calponin is mainly made up of α-helices with hydrogen bond turns.

Calmodulin, when activated by calcium may bind weakly to the CH domain and inhibit calponin binding with α-actin.

Calponin is also thought to negatively affect the bone making process due to being expressed in high amounts in osteoblasts.