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Background
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S100 protein is a type of low molecular weight protein found in vertebrates characterized by two calcium s of the helix-loop-helix ("EF-hand type") conformation. There are at least 21 different types of S100 proteins. The name is derived from the fact that the protein is 100 % Soluble in ammonium sulfate at neutral pH . Most S100 proteins are homodimeric, consisting of two identical polypeptides held together by non-covalent bonds. S100A is composed of an alpha and beta chain whereas S100B is composed of two beta chains. 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 Ca++ receptor widely expressed in many cells.S-100 is normally present in cells derived from the neural crest (Schwann cells, melanocytes, and glia cells), chondrocyte, adipocytes, myoepithelial cells, macrophages, Langerhans cells, dendritic cells, and keratinocytes. It may be present in some breast epithelial cells.Synonyms: Astrocyte Marker, S-100 protein, S-100 protein alpha chain, S-100 protein alpha subunit, S-100 protein beta chain, S-100 protein beta subunit, S100 Alpha, S100 Beta, S100 Calcium binding protein, S100A, S100B
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