The S-100 protein family consists of a group of calcium-binding proteins that are exclusively expressed in vertebrates and exhibit cell and tissue-specific expression. The expression levels of its members differ in various pathological conditions. The extracellular functions of the S-100 family may include the ability to enhance neurite outgrowth, involvement in inflammation and motility of tumor cells. S-100Z (S100 calcium-binding protein Z) is a 99 amino acid protein that shares 57% and 52% sequence identity with S-100A1 and S-100P, respectively. A dimeric, predominantly ?-helical protein, S-100Z contains two EF-hand domains capable of binding calcium ions. Binding of calcium results in conformational changes and exposure of hydrophobic surfaces on the protein. S-100Z interacts with S-100P, and demonstrates highest level of expression in spleen and leukocytes. The S-100Z gene is conserved in chimpanzee, bovine, mouse, rat, chicken and zebrafish, and maps to human chromosome 5q13.3.