S-100 protein is a family of low molecular weight protein found in vertebrates characterized by two calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 binding sites 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

Ammonium sulfate

Ammonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...

 at neutral pH

PH

In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

.

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

Calmodulin

Calmodulin is a calcium-binding protein expressed in all eukaryotic cells...

, 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

S100 is normally present in cells derived from the neural crest

Neural crest

Neural crest cells are a transient, multipotent, migratory cell population unique to vertebrates that gives rise to a diverse cell lineage including melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia....

 (Schwann cell

Schwann cell

Schwann cells or neurolemmocytes are the principal glia of the peripheral nervous system . Glial cells function to support neurons and in the PNS, also include satellite cells, olfactory ensheathing cells, enteric glia and glia that reside at sensory nerve endings, such as the Pacinian corpuscle...

s, melanocyte

Melanocyte

-External links: - "Eye: fovea, RPE" - "Integument: pigmented skin"...

s, and glial cell

Glial cell

Glial cells, sometimes called neuroglia or simply glia , are non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the brain, and for neurons in other parts of the nervous system such as in the autonomous nervous system...

s), chondrocyte

Chondrocyte

Chondrocytes are the only cells found in cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans...

s, adipocyte

Adipocyte

However, in some reports and textbooks, the number of fat cell increased in childhood and adolescence. The total number is constant in both obese and lean adult...

s, myoepithelial cells, macrophage

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

s, Langerhans cell

Langerhans cell

Langerhans cells are dendritic cells of the skin and mucosa, and contain large granules called Birbeck granules. They are present in all layers of the epidermis, but are most prominant in the stratum spinosum. They also occur in the papillary dermis, particularly around blood vessels, as well as...

s, dendritic cells, and keratinocytes. It may be present in some breast

Breast

The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...

 epithelial cells.

S100 proteins have been implicated in a variety of intracellular and extracellular functions. 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. S100A7 (psoriasin) and S100A15 have been found to act as cytokines in inflammation, particularly in autoimmune skin conditions such as psoriasis.

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

Melanoma

Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...

s, 50% of malignant peripheral nerve sheath tumor

Malignant peripheral nerve sheath tumor

A malignant peripheral nerve sheath tumor is a form of cancer of the connective tissue surrounding nerves. Given its origin and behavior it is classified as a sarcoma...

s, schwannomas, paraganglioma stromal cells, histiocytoma

Histiocytoma

A histiocytoma is a tumour consisting of histiocytes. Histiocytes are cells that are a part of the mononuclear phagocytic system, a part of the body's immune system that consists of phagocytic cells, which are responsible for engulfing solid particles by the cell membrane to form an internal...

 and clear cell sarcomas. Further, S100 proteins are markers for inflammatory diseases and can mediate inflammation and act as antimicrobials.

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

Human Genes

• S100A1
  S100A1
  S100 calcium-binding protein A1, also known as S100A1, is a protein which in humans is encoded by the S100A1 gene.- Function :The protein encoded by this gene is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs...
  
  , S100A2
  S100A2
  Protein S100-A2 is a protein that in humans is encoded by the S100A2 gene.-Further reading:...
  
  , S100A3
  S100A3
  Protein S100-A3 is a protein that in humans is encoded by the S100A3 gene.-Further reading:...
  
  , S100A4
  S100A4
  Protein S100-A4 is a protein that in humans is encoded by the S100A4 gene.-Interactions:S100A4 has been shown to interact with S100 calcium binding protein A1.-Further reading:...
  
  , S100A5
  S100A5
  Protein S100-A5 is a protein that in humans is encoded by the S100A5 gene.-Further reading:...
  
  , S100A6
  S100A6
  Protein S100-A6 is a protein that in humans is encoded by the S100A6 gene.-Interactions:S100A6 has been shown to interact with S100B and SUGT1.-Further reading:...
  
  , S100A7
  S100A7
  Protein S100-A7 also known as S100 calcium-binding protein A7 or psoriasin is a protein that in humans is encoded by the S100A7 gene.- Function :S100A7 is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs...
  
   psoriasin, S100A8, S100A9
  S100A9
  Protein S100-A9 also known as migration inhibitory factor-related protein 14 or calgranulin-B is a protein that in humans is encoded by the S100A9 gene.- Function :...
  
  , S100A10
  S100A10
  S100-A10, also known as p11, is a protein that is encoded by the S100A10 gene in humans and the S100a10 gene in other species. S100-A10 is a member of the S100 family of proteins containing two EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide...
  
  , S100A11
  S100A11
  Protein S100-A11 is a protein that in humans is encoded by the S100A11 gene.-Interactions:S100A11 has been shown to interact with Nucleolin and S100B.-Further reading:...
  
  , S100A12
  S100A12
  Protein S100-A12 is a protein that in humans is encoded by the S100A12 gene.-Further reading:...
  
  , S100A13
  S100A13
  Protein S100-A13 is a protein that in humans is encoded by the S100A13 gene.-Interactions:S100A13 has been shown to interact with SYT1 and FGF1.-Further reading:...
  
  , S100A14, S100A15
  S100A15
  Koebnerisin also known as protein S100-A7A , S100 calcium-binding protein A7-like 1 or S100 calcium-binding protein A15 is a protein that in humans is encoded by the S100A7A gene....
  
   Koebnerisin, , S100A16
  S100A16
  Protein S100-A16 is a protein that in humans is encoded by the S100A16 gene.-Further reading:...
  
  
• S100B
  S100B
  S100 calcium binding protein B or S100B is a protein of the S-100 protein family.S100 proteins are localized in the cytoplasm and nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation...
  
  
• S100P
  S100P
  Protein S100-P is a protein that in humans is encoded by the S100P gene.-Interactions:S100P has been shown to interact with EZR.-Further reading:...
  
  
• S100Z

CRNN; FLG

Filaggrin

Filaggrin is a filament-associated protein that binds to keratin fibers in epithelial cells.-Profilaggrin:Filaggrin monomers are tandemly clustered into a large, 350kDa protein precursor known as profilaggrin. In the epidermis, these structures are present in the keratohyalin granules in cells of...

; HRNR; IFPS

IFPS

IFPS was a financial modeling language created by professor Gerald R. Wagner and his students of the University of Texas at Austin in the late 1970s. IFPS was marketed by Execucom, an Austin-based company started by Wagner...

; RPTN

RPTN

RPTN is a gene that encodes repetin.Repetin is an extracellular epidermal matrix protein.It is one of the genes that differ between present-day humans and neandertals....

; S100G

S100G

Protein S100-G is a protein that in humans is encoded by the S100G gene.-Further reading:...

; TCHH; THHL1;