Annexin I, also known as lipocortin I (Lipo1), belongs to the family of annexins. These proteins are thought to control the biosynthesis of the potent mediators of inflammation, prostaglandins and leukotrienes. In two lipocortins (I and II) a short amino-terminal sequence distinct from the core structure has potential regulatory functions which are dependent on its phosphorylation state. The gene in the mouse encodes a protein of 346 amino acid residues. Mouse Lipo1 gene spans about 17 kb and is divided into 13 exons. Annexin I gene, mapped to 9q11-q22, is located on mouse chromosome 19. Annexin I acts through the formyl peptide receptor on human neutrophils. Peptides derived from the unique N-terminal domain of annexin I serve as FPR ligands and trigger different signaling pathways in a dose-dependent manner.