Calponin

Last updated
Calponin Homology Domain
1WYP.png
CH domain from H.Sapiends Calponin 1. PDB 1wyp
Identifiers
SymbolCH
Pfam PF00307
Pfam clan CL0188
InterPro IPR001715
calponin 1, basic, smooth muscle
1WYP.png
Solution structure of the CH domain of human Calponin 1. Rainbow colored cartoon (N-terminus = blue, C-terminus = red). [1]
Identifiers
SymbolCNN1
NCBI gene 1264
HGNC 2155
OMIM 600806
PDB 1WYP
RefSeq NM_001299
UniProt P51911
Other data
Locus Chr. 19 p13.2-13.1
calponin 2
Identifiers
SymbolCNN2
NCBI gene 1265
HGNC 2156
OMIM 602373
RefSeq NM_004368
UniProt Q99439
Other data
Locus Chr. 21 q11.1
calponin 3, acidic
Identifiers
SymbolCNN3
NCBI gene 1266
HGNC 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.

Contents

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

Related Research Articles

Calmodulin Calcium Modulated Protein

Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the binding of Ca2+ is required for the activation of calmodulin. Once bound to Ca2+, calmodulin acts as part of a calcium signal transduction pathway by modifying its interactions with various target proteins such as kinases or phosphatases.

Smooth muscle Involuntary non-striated muscle

Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations. It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit muscle, the whole bundle or sheet of smooth muscle cells contracts as a syncytium.

Actin Family of proteins

Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over 100 μM; its mass is roughly 42 kDa, with a diameter of 4 to 7 nm.

Myosin

Myosins are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility. The term was originally used to describe a group of similar ATPases found in the cells of both striated muscle tissue and smooth muscle tissue. Following the discovery by Pollard and Korn (1973) of enzymes with myosin-like function in Acanthamoeba castellanii, a global range of divergent myosin genes have been discovered throughout the realm of eukaryotes.

Muscle contraction Activation of tension-generating sites in muscle

Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding a heavy book or a dumbbell at the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state.

Voltage-gated calcium channels (VGCCs), also known as voltage-dependent calcium channels (VDCCs), are a group of voltage-gated ion channels found in the membrane of excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the calcium ion Ca2+. These channels are slightly permeable to sodium ions, so they are also called Ca2+-Na+ channels, but their permeability to calcium is about 1000-fold greater than to sodium under normal physiological conditions.

Tropomyosin Protein

Tropomyosin is a two-stranded alpha-helical, coiled coil protein found in actin-based cytoskeletons.

Actin-binding proteins are proteins that bind to actin. This may mean ability to bind actin monomers, or polymers, or both.

Myofilament The two protein filaments of myofibrils in muscle cells

Myofilaments are the two protein filaments of myofibrils in muscle cells. The two proteins are myosin and actin and are the contractile proteins involved in muscle contraction. The two filaments are a thick one composed mostly of myosin, and a thin one composed mostly of actin.

Nebulin

Nebulin is an actin-binding protein which is localized to the thin filament of the sarcomeres in skeletal muscle. It is a very large protein and binds as many as 200 actin monomers. Because its length is proportional to thin filament length, it is believed that nebulin acts as a thin filament "ruler" and regulates thin filament length during sarcomere assembly and acts as the coats the actin filament. Other functions of nebulin, such as a role in cell signaling, remain uncertain.

Telokin

Telokin is an abundant protein found in smooth-muscle. It is identical to the C-terminus of myosin light-chain kinase. Telokin may play a role in the stabilization of unphosphorylated smooth-muscle myosin filaments. Because of its origin as the C-terminal end of smooth muscle myosin light chain kinase, it is called "telokin".

Myosin light-chain kinase Class of kinase enzymes

Myosin light-chain kinase also known as MYLK or MLCK is a serine/threonine-specific protein kinase that phosphorylates a specific myosin light chain, namely, the regulatory light chain of myosin II.

Calmodulin-binding proteins are, as their name implies, proteins which bind calmodulin. Calmodulin can bind to a variety of proteins through a two-step binding mechanism, namely "conformational and mutually induced fit", where typically two domains of calmodulin wrap around an emerging helical calmodulin binding domain from the target protein.

Caldesmon

Caldesmon is a protein that in humans is encoded by the CALD1 gene.

Actin, alpha skeletal muscle

Actin, alpha skeletal muscle is a protein that in humans is encoded by the ACTA1 gene.

TPM1

Tropomyosin alpha-1 chain is a protein that in humans is encoded by the TPM1 gene. This gene is a member of the tropomyosin (Tm) family of highly conserved, widely distributed actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non-muscle cells.

Myosin-light-chain phosphatase

Myosin light-chain phosphatase, more commonly called myosin phosphatase, is an enzyme that dephosphorylates the regulatory light chain of myosin II. This dephosphorylation reaction occurs in smooth muscle tissue and initiates the relaxation process of the muscle cells. Thus, myosin phosphatase undoes the muscle contraction process initiated by myosin light-chain kinase. The enzyme is composed of three subunits: the catalytic region, the myosin binding subunit (MYPT1), and a third subunit (M20) of unknown function. The catalytic region uses two manganese ions as catalysts to dephosphorylate the light-chains on myosin, which causes a conformational change in the myosin and relaxes the muscle. The enzyme is highly conserved and is found in all organisms’ smooth muscle tissue. While it is known that myosin phosphatase is regulated by rho-associated protein kinases, there is current debate about whether other molecules, such as arachidonic acid and cAMP, also regulate the enzyme.

Troponin C type 1

Troponin C, also known as TN-C or TnC, is a protein that resides in the troponin complex on actin thin filaments of striated muscle and is responsible for binding calcium to activate muscle contraction. Troponin C is encoded by the TNNC1 gene in humans for both cardiac and slow skeletal muscle.

Calponin 2

Calponin 2 is a protein that in humans is encoded by the CNN2 gene.

Calponin 1

Calponin 1 is a basic smooth muscle protein that in humans is encoded by the CNN1 gene.

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}}: 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.