Ammonium ion transport by the AMT/Rh homolog TaAMT1;1 is stimulated by acidic pH
(2009) In Pflügers Archiv 458(4). p.43-733- Abstract
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... (More)It is unclear how ammonia is transported by proteins from the Amt/Mep/Rh
(Less)
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 NH3 and H+ via separate pathways but the latter two recombine before leaving the protein.
- author
- Søgaard, Rikke ; Alsterfjord, Magnus LU ; MacAulay, Nanna and Zeuthen, Thomas
- publishing date
- 2009-08
- type
- Contribution to journal
- publication status
- published
- keywords
- Animals, Biological Transport, Active/physiology, Cation Transport Proteins/chemistry, Cell Membrane/chemistry, Cells, Cultured, Hydrogen-Ion Concentration, Ion Channel Gating/physiology, Membrane Potentials/physiology, Oocytes/physiology, Plant Proteins/chemistry, Quaternary Ammonium Compounds/chemistry, Triticum/genetics, Xenopus laevis
- in
- Pflügers Archiv
- volume
- 458
- issue
- 4
- pages
- 11 pages
- publisher
- Springer
- external identifiers
-
- scopus:67649836535
- pmid:19340454
- ISSN
- 1432-2013
- DOI
- 10.1007/s00424-009-0665-z
- language
- English
- LU publication?
- no
- id
- 48288b4c-4ab0-4d76-ac4c-88dd36bad350
- date added to LUP
- 2025-08-14 10:01:35
- date last changed
- 2025-08-21 09:27:44
@article{48288b4c-4ab0-4d76-ac4c-88dd36bad350,
abstract = {{<p>It is unclear how ammonia is transported by proteins from the Amt/Mep/Rh<br>
superfamily. We investigated this for the ammonium transporter TaAMT1;1<br>
from wheat expressed in <i>Xenopus</i> oocytes by two-electrode voltage clamp and radio-labeled uptakes. Inward currents were activated by NH<br>
<sup>+</sup><sub>4</sub><br>
<br>
or methylammonium ions (MeA<sup>+</sup>). <br>
Importantly, currents increased fivefold when the external pH was <br>
decreased from 7.4 to 5.5; this type of pH dependence is unique and is a<br>
strong indication of NH<br>
<sup>+</sup><sub>4</sub><br>
<br>
or MeA<sup>+</sup> transport. This was confirmed by the close correlation between the uptake of radio-labeled MeA<sup>+</sup> and MeA<sup>+</sup>-induced<br>
currents. Homology models of members of the Amt/Mep/Rh superfamily <br>
exhibited major divergences in their cytoplasmic regions. A point <br>
mutation in this region of TaAMT1;1 abolished the pH sensitivity and <br>
decreased the apparent affinities for NH<br>
<sup>+</sup><sub>4</sub><br>
<br>
and MeA<sup>+</sup>. We suggest a model where NH<br>
<sup>+</sup><sub>4</sub><br>
<br>
is transported as NH<sub>3</sub> and H<sup>+</sup> via separate pathways but the latter two recombine before leaving the protein.</p>}},
author = {{Søgaard, Rikke and Alsterfjord, Magnus and MacAulay, Nanna and Zeuthen, Thomas}},
issn = {{1432-2013}},
keywords = {{Animals; Biological Transport, Active/physiology; Cation Transport Proteins/chemistry; Cell Membrane/chemistry; Cells, Cultured; Hydrogen-Ion Concentration; Ion Channel Gating/physiology; Membrane Potentials/physiology; Oocytes/physiology; Plant Proteins/chemistry; Quaternary Ammonium Compounds/chemistry; Triticum/genetics; Xenopus laevis}},
language = {{eng}},
number = {{4}},
pages = {{43--733}},
publisher = {{Springer}},
series = {{Pflügers Archiv}},
title = {{Ammonium ion transport by the AMT/Rh homolog TaAMT1;1 is stimulated by acidic pH}},
url = {{http://dx.doi.org/10.1007/s00424-009-0665-z}},
doi = {{10.1007/s00424-009-0665-z}},
volume = {{458}},
year = {{2009}},
}