Ammonium ion transport by the AMT/Rh homolog TaAMT1;1 is stimulated by acidic pH
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Ammonium ion transport by the AMT/Rh homolog TaAMT1;1 is stimulated by acidic pH. / Søgaard, Rikke; Alsterfjord, Magnus; Macaulay, Nanna; Zeuthen, Thomas.
In: Pflügers Archiv: European Journal of Physiology, Vol. 458, No. 4, 2009, p. 733-43.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Ammonium ion transport by the AMT/Rh homolog TaAMT1;1 is stimulated by acidic pH
AU - Søgaard, Rikke
AU - Alsterfjord, Magnus
AU - Macaulay, Nanna
AU - Zeuthen, Thomas
PY - 2009
Y1 - 2009
N2 - It is unclear how ammonia is transported by proteins from the Amt/Mep/Rh superfamily. We investigated this for the ammonium transporter TaAMT1;1 from wheat expressed in Xenopus oocytes by two-electrode voltage clamp and radio-labeled uptakes. Inward currents were activated by NH (4) (+) or methylammonium ions (MeA(+)). Importantly, currents increased fivefold when the external pH was decreased from 7.4 to 5.5; this type of pH dependence is unique and is a strong indication of NH (4) (+) or MeA(+) transport. This was confirmed by the close correlation between the uptake of radio-labeled MeA(+) and MeA(+)-induced currents. Homology models of members of the Amt/Mep/Rh superfamily exhibited major divergences in their cytoplasmic regions. A point mutation in this region of TaAMT1;1 abolished the pH sensitivity and decreased the apparent affinities for NH (4) (+) and MeA(+). We suggest a model where NH (4) (+) is transported as NH(3) and H(+) via separate pathways but the latter two recombine before leaving the protein.
AB - It is unclear how ammonia is transported by proteins from the Amt/Mep/Rh superfamily. We investigated this for the ammonium transporter TaAMT1;1 from wheat expressed in Xenopus oocytes by two-electrode voltage clamp and radio-labeled uptakes. Inward currents were activated by NH (4) (+) or methylammonium ions (MeA(+)). Importantly, currents increased fivefold when the external pH was decreased from 7.4 to 5.5; this type of pH dependence is unique and is a strong indication of NH (4) (+) or MeA(+) transport. This was confirmed by the close correlation between the uptake of radio-labeled MeA(+) and MeA(+)-induced currents. Homology models of members of the Amt/Mep/Rh superfamily exhibited major divergences in their cytoplasmic regions. A point mutation in this region of TaAMT1;1 abolished the pH sensitivity and decreased the apparent affinities for NH (4) (+) and MeA(+). We suggest a model where NH (4) (+) is transported as NH(3) and H(+) via separate pathways but the latter two recombine before leaving the protein.
U2 - 10.1007/s00424-009-0665-z
DO - 10.1007/s00424-009-0665-z
M3 - Journal article
C2 - 19340454
VL - 458
SP - 733
EP - 743
JO - Pflügers Archiv - European Journal of Physiology
JF - Pflügers Archiv - European Journal of Physiology
SN - 0031-6768
IS - 4
ER -
ID: 14334795