[Water channel family proteins].

17 members of MIP family from bacteria, yeast, plants and animals are compared in this review. These proteins appear to function in (1) water channels (CHIP, WCH-CD, MIWC, AQP3, gTIP, RD28, TobRB7), (2) neurogenesis (Bib), (3) small-molecule-permeating channels (MIP, AQP3, NOD, Glpf), (4) unknown function (WCH-3, AtRB7, Pea R7A, FPS1). However, the biological functions are not well established. The most conserved residues in the first and the second halves of all MIP family proteins are asparagine-proline-alanine (NPA) sequences in the loops (NPA boxes). This structural similarity may lead to functional similarity (water and/or small molecule permeation). This signature sequence for the MIP family will facilitate the identification of new protein members of this family.