Major intrinsic proteins

Major intrinsic proteins comprise a large superfamily of transmembrane protein channels that are grouped together on the basis of homology. The MIP superfamily includes three subfamilies: aquaporins, aquaglyceroporins and S-aquaporins.

1. The aquaporins (AQPs) are water selective.
2. The aquaglyceroporins are permeable to water, but also to other small uncharged molecules such as glycerol.
3. The third subfamily, with little conserved amino acid sequences around the NPA boxes, include 'superaquaporins' (S-aquaporins).

The phylogeny of insect MIP family channels has been published.