S100 family proteins are small (10-12 kDa), acidic proteins that are found exclusively in vertebrates. They belong to a highly conserved group of EF-hand calcium-binding molecules that consists of more than 25 members. They are the only EF-hand proteins that form both homodimeric and heterodimeric complexes. Although structurally related, their expression patterns and functions are usually distinct.
S100A16 (also S100F) is a 12 kDa member of the S100 family, EF-hand superfamily of Ca2+-binding proteins. By Northern blot, S100A16 is found in multiple tissue types; in brain, it is specifically found in astrocytes. Intracellularly, S100A16 is both nuclear and cytoplasmic and apparently exists as a homodimer, trimer, and tetramer. Human S100A16 is 103 amino acids (aa) in length. It contains two EF-hand motifs (aa 12 - 47 and 54 - 89) with only one high-affinity Ca2+-binding site (aa 67 - 78) and is believed to undergo phosphorylation at Ser103. Full-length human S100A16 shares 90% and 72% aa identity with canine and mouse S100A16, respectively.