S100 calcium binding protein A10, also known S100A10, 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. S100A10 is primarily found in mast cells as heterotetrameric complexes that are present intracellularly at the plasma membrane or on the extracellular cell surface.