– Protein S100-P (S100P) belongs to the S100 family of Calcium-Binding Proteins. S100P is 95 amino acids in length and it contains 2 EF-Hand Calcium-Binding Motifs. The EF-Hand Motif binds calcium, which likely alters molecular conformation. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells and it is involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. In addition to binding Ca, S100P also binds Zn and Mg, and may play a role in the etiology of prostate cancer.