S100A10,also known as p11,is a member of the S100 family of small,EF hand containing dimeric proteins. S100 proteins are localized in the cytoplasm and/or 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 present on the surface of endothelial and other cells in a heterotetrameric complex with another Ca(2+)-binding protein,annexin II. S100A10 may function in exocytosis and endocytosis.