Aquaporin homologues in plants and mammals transport ammonia. FEBS Lett

IT University of Copenhagen, København, Capital Region, Denmark
FEBS Letters (Impact Factor: 3.17). 10/2004; 574(1-3):31-6. DOI: 10.1016/j.febslet.2004.08.004
Source: PubMed


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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Available from: Dan Arne Klaerke,
    • "It is proposed that the interaction with GS creates a metabolic channel to aid assimilation of fixed nitrogen and prevent futile cycling of ammonia (Masalkar et al., 2010). It is interesting to note that other members of the superfamily, such as Arabidopsis tonoplast intrinsic protein (TIP) family, and mammalian AQP1 and AQP8 also transport ammonia (Jahn et al., 2004; Loqué et al., 2005; Zeuthen et al., 2009). Earlier studies on Nodulin 26 suggested that Nodulin 26 has high permeability to water and also transports glycerols and formamide (Dean et al., 1999; Guenther et al., 2003; Rivers et al., 1997), and that its permeability may be regulated by phosphorylation (Weaver and Roberts, 1992). "
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    • "Even neutral , protonated arsenous (Liu et al., 2002; Wu et al., 2010) and silicic acid (Ma et al., 2006) have been found to pass. Further substrates of AQPs are solubilized gasses, namely ammonia (Jahn et al., 2004; Zeuthen et al., 2006) and carbon dioxide (Nakhoul et al., 1998). Especially the latter has been linked to permeation through the central pore (Musa-Aziz et al., 2009). "
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    • "Cytosolic NH 3 is passively transported through the tonoplast as the acidic environment traps NH 3 as NH 4 + . TIPs have been shown to play a role in NH 3 import into the vacuole ( Jahn et al., 2004; Loqué et al., 2005). "
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