S100b is a member of the S100 family of proteins which are a family of EF-hand calcium binding proteins that exist mostly as dimers of the 20 currently identified individual S100 monomers. The S100B homodimer is expressed in cells of the central nervous system， glial cells and in certain peripheral cells e.g. Schwann cells， melanocytes， adipocytes and chondrocytes. S100 proteins are localized either in the cytoplasm or the nucleus of a wide range of cells. S100 proteins are involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. There are at least 13 members in the S100 gene family， which are located as a cluster on chromosome 1q21； however， S100b is located at 21q22.3. The determination of S100B in serum levels may be used to monitor the extent of brain injury and malignant melanoma. S100b proteins may have a role in Neurite extension， proliferation of melanoma cells， stimulation of Ca2+ fluxes， inhibition of PKC-mediated phosphorylation， astrocytosis and axonal proliferation， and inhibition of microtubule assembly. Chromosomal rearrangements and altered expression of the S100b gene are implicated in several neurological， neoplastic， and other types of diseases， including Alzheimer’s disease， Down’s syndrome， epilepsy， amyotrophic lateral sclerosis， melanoma， and type I diabetes.
