S100 calcium-binding protein A10 (S100A10), also known as p11, is a protein that is encoded by the S100A10 gene in humans and the S100a10 gene in other species. S100A10 is a member of the S100 family of proteins containing two EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells. They regulate a number of cellular processes such as cell cycle progression and differentiation. The S100 protein is implicated in exocytosis and endocytosis by reorganization of F-actin.