Article

Aquaporin homologues in plants and mammals transport ammonia.

Plant Nutrition Laboratory, Department of Agricultural Sciences, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
FEBS Letters (Impact Factor: 3.34). 10/2004; 574(1-3):31-6.
Source: PubMed

ABSTRACT Using functional complementation and a yeast mutant deficient in ammonium (NH4+) transport (Deltamep1-3), three wheat (Triticum aestivum) TIP2 aquaporin homologues were isolated that restored the ability of the mutant to grow when 2 mM NH4+ was supplied as the sole nitrogen source. When expressed in Xenopus oocytes, TaTIP2;1 increased the uptake of NH4+ analogues methylammonium and formamide. Furthermore, expression of TaTIP2;1 increased acidification of the oocyte-bathing medium containing NH4+ in accordance with NH3 diffusion through the aquaporin. Homology modeling of TaTIP2;1 in combination with site directed mutagenesis suggested a new subgroup of NH3-transporting aquaporins here called aquaammoniaporins. Mammalian AQP8 sharing the aquaammoniaporin signature also complemented NH4+ transport deficiency in yeast.

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