MIP (Major Intrinsic Protein) family proteins exhibit essentially two distinct types of channel properties: (1) specific water transport by the aquaporins, and (2) small neutral solutes transport, such as glycerol by the glycerol facilitators [1].

1: Prediction of functional residues in water channels and related proteins. Froger A, Tallur B, Thomas D, Delamarche C; Protein Sci 1998;7:1458-1468. PMID:9655351