The Annexins are a family of structurally similar proteins. Annexins bind to phospholipids and may be involved in regulation of membrane transport, membrane channel activity, and interaction of the cell membrane with the extracellular matrix. Annexin A4 (ANXA4) belongs to the annexin family of calcium dependent phospholipid binding proteins. Although their functions are still not clearly defined, several members of the annexin family have been implicated in membrane related events along exocytotic and endocytotic pathways. ANXA4 has 45 to 59% identity with other members of its family and shares a similar size and exon intron organization. Isolated from human placenta, ANXA4 encodes a protein that has possible interactions with ATP, and has in vitro anticoagulant activity and also inhibits phospholipase A2 activity. ANXA4 is almost exclusively expressed in epithelial cells.