<p>The annexins (or lipocortins) are a family of proteins that bind to phospholipids in a calcium-dependent manner [<cite idref="PUB00001395"/>]. They are distributed ubiquitously in different tissues and cell types of higher and lower eukaryotes, including mammals, fish, birds, <taxon tax_id="7227">Drosophila melanogaster</taxon> (Fruit fly), <taxon tax_id="8355">Xenopus laevis</taxon> (African clawed frog), <taxon tax_id="6239">Caenorhabditis elegans</taxon>, <taxon tax_id="44689">Dictyostelium discoideum</taxon> (Slime mold) and <taxon tax_id="5141">Neurospora crassa</taxon> [<cite idref="PUB00013921"/>, <cite idref="PUB00013922"/>]. Annexins are absent from yeasts and prokaryotes [<cite idref="PUB00015121"/>]. The plant annexins are somewhat distinct from those found in other taxa [<cite idref="PUB00013922"/>].</p><p>Most eukaryotic species have 1-20 annexin (ANX) genes. All annexins share a core domain made up of four similar repeats, each approximately 70 amino acids long [<cite idref="PUB00001395"/>]. Each individual annexin repeat (sometimes referred to as endonexin folds) is folded into five alpha-helices, and in turn are wound into a right-handed super-helix; they usually contain a characteristic 'type 2' motif for binding calcium ions with the sequence 'GxGT-[38 residues]-D/E'. Animal and fungal annexins also have variable amino-terminal domains. The core domains of most vertebrate annexins have been analysed by X-ray crystallography, revealing conservation of their secondary and tertiary structures despite only 45-55% amino-acid identity among individual members. The four repeats pack into a structure that resembles a flattened disc, with a slightly convex surface on which the Ca 2+ -binding loops are located and a concave surface at which the amino and carboxyl termini come into close apposition.</p><p>Annexins are traditionally thought of as calcium-dependent phospholipid-binding proteins, but recent work suggests a more complex set of functions. The famiy has been linked with inhibition of phospholipase activity, exocytosis and endoctyosis, signal transduction, organisation of the extracellular matrix, resistance to reactive oxygen species and DNA replication [<cite idref="PUB00013921"/>].</p>