Journal of Biological Chemistry
Volume 273, Issue 38, 18 September 1998, Pages 24737-24743
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NUCLEIC ACIDS, PROTEIN SYNTHESIS, AND MOLECULAR GENETICS
Molecular Characterization of a Broad Selectivity Neutral Solute Channel*

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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.

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*

This work was supported in part by National Institutes of Health Grants DK46289 (to M. A. H.) and DK32753 (to W. B. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AF016406.

Supported by a Research Fellowship of the National Kidney Foundation.

§

Supported by the Siriraj-China Medical Board, Mahidol University, Thailand.

Samuel A. Levine Fellow of the American Heart Association, Massachusetts Affiliate.

Supported by National Institutes of Health Grant DK38452 (to Dr. Dennis Brown).