View source for Calmodulin

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[[Image:Calmodulin.png|thumb|left|200px|Calmodulin 3D structure]]
[[image:Flexibility of Calmodulin.png|thumb|left|200px|Flexibility of Calmodulin. Calmodulin can bind to calmodulin-dependent-protein kinase II-alpha (upper left, PDB code=1cm1); it can bind to myosine light chain (lower left, 2bbm); it can bind to edema factor toxin from the anthrax bacteria (right, 1k93)
[http://www.pdb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb44_1.html more details...]]]

==Overview==
'''Calmodulin''' ('''CaM''') (an abbreviation for '''CAL'''cium '''MODUL'''ated prote'''IN''') is a calcium-binding protein expressed in all [[eukaryotic]] cells.  It can bind to and regulate a number of different protein targets, thereby affecting many different cellular functions.<ref name="pmid6313166">{{cite journal | author = Stevens FC | title = Calmodulin: an introduction | journal = Can. J. Biochem. Cell Biol. | volume = 61 | issue = 8 | pages = 906-10 | year = 1983 | pmid = 6313166 | doi = | issn = }}</ref><ref name="pmid10884684">{{cite journal | author = Chin D, Means AR | title = Calmodulin: a prototypical calcium sensor | journal = Trends Cell Biol. | volume = 10 | issue = 8 | pages = 322-8 | year = 2000 | pmid = 10884684 | doi = 10.1016/S0962-8924(00)01800-6  | issn = }}</ref>  

==Function==
CaM mediates processes such as inflammation, metabolism, apoptosis, muscle contraction, intracellular movement, short-term and long-term memory, nerve growth and the immune response.  CaM is expressed in many cell types and can have different subcellular locations, including the cytoplasm, within organelles, or associated with the plasma or organelle membranes.  Many of the proteins that CaM binds are unable to bind calcium themselves, and as such use CaM as a calcium sensor and signal transducer.  CaM can also make use of the calcium stores in the endoplasmic reticulum, and the sarcoplasmic reticulum.  CaM undergoes a conformational change upon binding to calcium, which enables it to bind to specific proteins for a specific response. CaM can bind up to four calcium ions, and can undergo post-translational modifications, such as phosphorylation, acetylation, methylation and proteolytic cleavage, each of which can potentially modulate its actions. Calmodulin can also bind to [[Anthrax toxin|edema factor toxin]] from the [[anthrax]] bacteria. 

==Structure==
Calmodulin is a small, [[acid]]ic protein approximately 148 [[amino acid]]s long (16706 [[Atomic mass unit|Dalton]]) and, as such, is a favorite for testing [[computational chemistry|protein simulation software]]. It contains four [[EF-hand]] "[[structural motif|motifs]]", each of which binds a Ca<sup>2+</sup> ion. The protein has two approximately symmetrical domains, separated by a flexible "hinge" region. 

==Mechanism==
Calcium is bound via the use of the EF hand motif, which supplies an electronegative environment for ion coordination. After calcium binding, hydrophobic methyl groups from methionine residues become exposed on the protein via conformational change. This presents hydrophobic surfaces, which can in turn bind to Basic Amphiphilic Helices (BAA helices) on the target protein. These helices contain complementary hydrophobic regions. The flexibilily of Calmodulin's hinged region allows the molecule to "wrap around" its target. This property allows it to tightly bind to a wide range of different target proteins.

==Family members==
* [[Calmodulin 1]] ({{Gene|CALM1}})
* [[CALM2|Calmodulin 2]] ({{Gene|CALM2}})
* [[CALM3|Calmodulin 3]] ({{Gene|CALM3}})
* Calmodulin-like 1 ({{Gene|CALML1}})
* [[CALML3|Calmodulin-like 3]] ({{Gene|CALML3}})
* Calmodulin-like 4 ({{Gene|CALML4}})
* [[CALML5|Calmodulin-like 5]] ({{Gene|CALML5}})
* Calmodulin-like 6 ({{Gene|CALML6}})

== Other calcium-binding proteins ==

Calmodulin belongs to one of the two main groups of [[calcium]]-binding proteins, called EF hand proteins. The other group, called [[annexin]]s, bind calcium and [[phospholipid]] (e.g., [[lipocortin]]). Many other proteins bind calcium, although binding calcium may not be considered their principal function in the cell.

==See also==
*[[Protein kinase]]
*[[Ca2+/calmodulin-dependent protein kinase]]
*Douglas Stirling

==References==
{{Reflist|2}}

==External links==
* {{MeshName|Calmodulin}}
* {{InterPro|IPR015754}}
* {{cite web | url = http://www.ebi.ac.uk/interpro/potm/2003_3/Page_1.htm | title = Calmodulin | accessdate = 2008-03-22 | author = Jennifer McDowall | authorlink = | coauthors = | date = 2003-01-01 | format = | work = | publisher = InterPro Protein Archive | pages = | language = | archiveurl = | archivedate = | quote = }}
* {{cite web | url = http://structbio.vanderbilt.edu/cabp_database/general/prot_pages/calmod.html | title = Home Page for Calmodulin | accessdate = 2008-03-22 | author =  Melanie Nelson | authorlink = | coauthors = Walter Chazin | date = | format = | work =  EF-Hand Calcium-Binding Proteins Data Library | publisher = Vanderbilt University | pages = | language = | archiveurl = | archivedate = | quote = }}
* {{cite web | url = http://calcium.uhnres.utoronto.ca/ctdb/ctdb/home.html | title = Calmodulin Target Database | accessdate = 2008-03-22 | author = Mitsuhiko Ikura | authorlink = | coauthors = | date = | format = | work = | publisher = Ontario Cancer Institute, University of Toronto | pages = | language = | archiveurl = | archivedate = | quote = }}

{{Muscle tissue}}
{{Calcium-binding proteins}}


[[Category:Proteins]]
[[Category:Cell signaling]]
[[Category:Signal transduction]]
[[Category:Calcium signaling]]

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