The aquaporins (AQP), also known as the major intrinsic protein superfamily (MIP), are a family of integral membrane proteins. In mammals, 13 aquaporins were described (AQP0 – AQP12). Aquaporin 11 (AQP11) is a newly described member of the aquaporins family. Aquaporin-11 (AQP-11) has been identified with unusual pore-forming NPA (asparagine-proline-alanine) boxes. AQP-11 presents a conserved structure of six transmembrane domains with intracellular N- and C-termini. The functional channel is a tetramer but each subunit has a separate pore and therefore the functional channel unit, contains four pores1. There are two subfamilies: the aquaporins, which transport only water and the aquaglyceroporins, which transport glycerol, urea, and other small solutes in addition to water
