May associate with CD21. May regulate the release of Ca(2+) from intracellular stores (By similarity). Cytoplasmic in lung alveolar endothelial cells. In the lung, expressed by alveolar endothelial cells. Not expressed in tracheal endothelium or alveolar macrophages. A pair of annexin repeats may form one binding site for calcium and phospholipid. The N-terminus is blocked. Seems to bind one calcium ion with high affinity. Belongs to the annexin family.