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'''S-100 protein''' is a family of low molecular weight protein found in vertebrates characterized by two [[calcium]] binding sites of the [[helix-loop-helix]] ("[[EF-hand]] type") conformation. There are at least 21 different types of S100 proteins.<ref name="pmid15336958">{{cite journal | author = Marenholz I, Heizmann CW, Fritz G | title = S100 proteins in mouse and man: from evolution to function and pathology (including an update of the nomenclature) | journal = Biochem. Biophys. Res. Commun. | volume = 322 | issue = 4 | pages = 1111–22 | year = 2004 | month = October | pmid = 15336958 | doi = 10.1016/j.bbrc.2004.07.096 | url = }}</ref> The name is derived from the fact that the protein is ''100''% '''S'''oluble in [[ammonium sulfate]] at neutral [[pH]].

==Structure==

Most S100 proteins are homodimeric, consisting of two identical polypeptides held together by non-covalent bonds. Although S100 proteins are structurally similar to [[calmodulin]], they differ in that they are cell-specific, expressed in particular cells at different levels depending on environmental factors. To contrast, calmodulin is a ubiquitous and universal intracellular Ca²⁺ receptor widely expressed in many cells.

==Normal function==

S-100 is normally present in cells derived from the [[neural crest]] ([[Schwann cell]]s, [[melanocyte]]s, and [[glial cell]]s), [[chondrocyte]]s, [[adipocyte]]s, [[myoepithelial cell]]s, [[macrophage]]s, [[Langerhans cell]]s, [[dendritic cells]], and keratinocytes. It may be present in some [[breast]] epithelial cells.

S100 proteins have been implicated in a variety of intracellular and extracellular functions.<ref name="pmid12645002">{{cite journal | author = Donato R | title = Intracellular and extracellular roles of S100 proteins | journal = Microsc. Res. Tech. | volume = 60 | issue = 6 | pages = 540–51 | year = 2003 | month = April | pmid = 12645002 | doi = 10.1002/jemt.10296 | url = }}</ref> S100 proteins are involved in regulation of protein phosphorylation, transcription factors, Ca++ homeostasis, the dynamics of cytoskeleton constituents, enzyme activities, cell growth and differentiation, and the inflammatory response.

==Pathology==

Several members of the S-100 protein family are useful as markers for certain tumors and epidermal differentiation. It can be found in [[melanoma]]s,<ref name="pmid18547346">{{cite journal |author=Nonaka D, Chiriboga L, Rubin BP |title=Differential expression of S100 protein subtypes in malignant melanoma, and benign and malignant peripheral nerve sheath tumors |journal=J. Cutan. Pathol. |volume=35 |issue=11 |pages=1014–9 |year=2008 |month=November |pmid=18547346 |doi=10.1111/j.1600-0560.2007.00953.x}}</ref> 50% of [[malignant peripheral nerve sheath tumor]]s, schwannomas, paraganglioma stromal cells and [[clear cell sarcoma]]s.

S100 proteins have been used in the lab as cell markers for [[anatomic pathology]].

==Genes==

* [[S100A1]], [[S100A2]], [[S100A3]], [[S100A4]], [[S100A5]], [[S100A6]], [[S100A7]], [[S100A8]], [[S100A9]], [[S100A10]], [[S100A11]], [[S100A12]], [[S100A13]], [[S100A14]]({{Gene|S100A14}}), [[S100A15]]({{Gene|S100A15}}), [[S100A16]]

* [[S100B]]

* [[S100P]]

* [[S100Z]]({{Gene|S100Z}})

==References==

{{Reflist}}

== Further reading ==

* {{cite journal |author=Wolf R, Voscopoulos CJ, FitzGerald PC, ''et al.'' |title=The mouse S100A15 ortholog parallels genomic organization, structure, gene expression, and protein-processing pattern of the human S100A7/A15 subfamily during epidermal maturation |journal=J. Invest. Dermatol. |volume=126 |issue=7 |pages=1600–8 |year=2006 |pmid=16528363 |doi=10.1038/sj.jid.5700210}}

==External links==

* {{MeshName|S100+Proteins}}

{{Calcium-binding proteins}}

{{Nerve tissue protein}}

{{Tumor markers}}

[[Category:Anatomical pathology]]

[[Category:Proteins]]

{{pathology-stub}}

[[de:S-100-Protein]]

[[it:S-100 (biologia)]]

[[pl:Białka S-100]]

[[ru:Белок S100]]