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Calponin Homology Domain
CH domain from H.Sapiends Calponin 1. PDB 1wyp
Symbol CH
Pfam PF00307
Pfam clan CL0188
InterPro IPR001715
calponin 1, basic, smooth muscle
Solution structure of the CH domain of human Calponin 1. Rainbow colored cartoon (N-terminus = blue, C-terminus = red).[1]
Symbol CNN1
Entrez 1264
HUGO 2155
OMIM 600806
RefSeq NM_001299
UniProt P51911
Other data
Locus Chr. 19 p13.2-13.1
calponin 2
Symbol CNN2
Entrez 1265
HUGO 2156
OMIM 602373
RefSeq NM_004368
UniProt Q99439
Other data
Locus Chr. 21 q11.1
calponin 3, acidic
Symbol CNN3
Entrez 1266
HUGO 2157
OMIM 602374
RefSeq NM_001839
UniProt Q6FHA7
Other data
Locus Chr. 1 p22-p21

Calponin is a calcium binding protein. 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.

Structure and function[edit]

Calponin is mainly made up of α-helices with hydrogen bond turns. It is a binding protein and is made up of three domains. These domains in order of appearance are Calponin Homology (CH), regulatory domain (RD), and Click-23, domain that contains the calponin repeats. At the CH domain calponin binds to α-actin and filamin and binds to actin within the RD domain. Calmodulin, when activated by calcium may bind weakly to the CH domain and inhibit calponin binding with α-actin.[2] Calponin is responsible for binding many actin binding proteins, phospholipids, and regulates the actin/myosin interaction. Calponin is also thought to negatively affect the bone making process due to being expressed in high amounts in osteoblasts.[3]


  1. ^ PDB: 1WYP​; Tomizawa T, Kigawa T, Koshiba S, Inoue M, Yokoyama S. "RCSB PDB - 1WYP Structure Summary". RCSB Protein Data Bank. doi:10.2210/pdb1wyp/pdb. 
  2. ^ Ferjani, I; Fattoum, A; Manai, M; Benyamin, Y; Roustan, C; Maciver, SK (September 2010). "Two distinct regions of calponin share common binding sites on actin resulting in different modes of calponin-actin interaction.". Biochimica et Biophysica Acta. 1804 (9): 1760–7. doi:10.1016/j.bbapap.2010.05.012. PMID 20595006. 
  3. ^ Maciver S. "The Calponin Family". Department of Biomedical Sciences, University of Edinburgh. Retrieved 2011-04-25. 

External links[edit]