Molecular characterization of a broad selectivity neutral solute channel

J Biol Chem. 1998 Sep 18;273(38):24737-43. doi: 10.1074/jbc.273.38.24737.


In all living cells, coordination of solute and water movement across cell membranes is of critical importance for osmotic balance. The current concept is that these processes are of distinct biophysical nature. Here we report the expression cloning of a liver cDNA encoding a unique promiscuous solute channel (AQP9) that confers high permeability for both solutes and water. AQP9 mediates passage of a wide variety of non-charged solutes including carbamides, polyols, purines, and pyrimidines in a phloretin- and mercury-sensitive manner, whereas amino acids, cyclic sugars, Na+, K+, Cl-, and deprotonated monocarboxylates are excluded. The properties of AQP9 define a new evolutionary branch of the major intrinsic protein family of aquaporin proteins and describe a previously unknown mechanism by which a large variety of solutes and water can pass through a single pore, enabling rapid cellular uptake or exit of metabolites with minimal osmotic perturbation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Aquaporin 1
  • Aquaporin 3
  • Aquaporins*
  • Cloning, Molecular
  • Female
  • Ion Channels / chemistry*
  • Ion Channels / genetics
  • Ion Channels / physiology*
  • Liver / metabolism*
  • Membrane Potentials / drug effects
  • Models, Molecular
  • Molecular Sequence Data
  • Oocytes / physiology
  • Osmolar Concentration
  • Phloretin / pharmacology
  • Protein Structure, Secondary*
  • RNA, Messenger / biosynthesis
  • Rats
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Transcription, Genetic
  • Xenopus laevis


  • Aqp1 protein, rat
  • Aqp3 protein, rat
  • Aqp9 protein, rat
  • Aquaporins
  • Ion Channels
  • RNA, Messenger
  • Recombinant Proteins
  • Aquaporin 1
  • Aquaporin 3
  • Phloretin

Associated data

  • GENBANK/AF016406