S100 calcium binding protein A16, also known S100A16, is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. 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. Intracellularly, S100A16 is both nuclear and cytoplasmic and apparently exists as a homodimer, trimer and tetramer.