Calponin

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.

Calponin Homology Domain
CH domain from H.Sapiends Calponin 1. PDB 1wyp
Identifiers
SymbolCH
PfamPF00307
Pfam clanCL0188
InterProIPR001715
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]
Identifiers
SymbolCNN1
NCBI gene1264
HGNC2155
OMIM600806
PDB1WYP
RefSeqNM_001299
UniProtP51911
Other data
LocusChr. 19 p13.2-13.1
calponin 2
Identifiers
SymbolCNN2
NCBI gene1265
HGNC2156
OMIM602373
RefSeqNM_004368
UniProtQ99439
Other data
LocusChr. 21 q11.1
calponin 3, acidic
Identifiers
SymbolCNN3
NCBI gene1266
HGNC2157
OMIM602374
RefSeqNM_001839
UniProtQ6FHA7
Other data
LocusChr. 1 p22-p21

Structure and function

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]

Immunohistochemistry for calponin in ductal carcinoma in situ, highlighting myoepithelial cells around all tumor cells, thereby ruling out invasive ductal carcinoma.

References
  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. Cite journal requires |journal= (help)
  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 (BBA) - Proteins and Proteomics. 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.


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