Aquaporin homologues in plants and mammals transport ammonia.
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.
Jahn
Thomas P
TP
Plant Nutrition Laboratory, Department of Agricultural Sciences, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark. tpj@kvl.dk
Møller
Anders L B
AL
Zeuthen
Thomas
T
Holm
Lars M
LM
Klaerke
Dan A
DA
Mohsin
Brigitte
B
Kühlbrandt
Werner
W
Schjoerring
Jan K
JK
D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D003001:Cloning, Molecular; D017931:DNA Primers; D005816:Genetic Complementation Test; D016297:Mutagenesis, Site-Directed; D010944:Plants / Q000378:metabolism*
D020346:Aquaporins; D017931:DNA Primers; D000641:Ammonia