Calponin 1, Basic (CNN1)

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 thought to play a role in smooth muscle contraction. These are the products of separate loci. Northern blots of mouse uterus RNA indicated that h1 transcripts are about 10-fold higher than those of the h2 gene.

The 297-amino acid CNN1 contains a motif that is tandemly repeated 3 times. The N terminus of CNN1 is markedly basic and highly homologous to that of CNN3. CNN1 has a predicted pI of 9.4. Northern blot analysis of RNA from human tissues showed that CNN1 is specifically expressed in smooth muscle.