S-100B is a member of highly homologous Ca2 binding proteins family that possess two EF-hand motifs. The family of S100 proteins consists of 19 members. Most S100 proteins exist as dimers (frequently homodimers) within cells. Exclusively expressed in vertebrates, S100 is implicated in various intracellular and extracellular regulatory activities.

Studies indicate that S100 proteins are involved in the inhibition of protein phosphorylation, inhibition of cytosceletal constituent assembly, regulation of Ca2 homeostasis, stimulation of enzyme activities, and interaction with transcription factors. S100B is abundant in the nervous system where it is predominantly expressed in astrocytes, oligodendrocytes and Schwann cells.