Ammonium ion transport by the AMT/Rh homolog LeAMT1;1

Maria Mayer , Marek Dynowski , Uwe Ludewig (1)

1 Pflanzenphysiologie

AMT/Rh ammonium transporters/channels are identified in all domains of life and fulfill contrasting functions related either to ammonium acquisition or excretion. Based on functional and crystallographic high-resolution structural data, it was recently proposed that the bacterial AmtB is a gas channel for NH 3}. Key residues, proposed to be crucial for NH 3} conduction, and the hydrophobic, but obstructed pore, were conserved in a homology model of LeAMT1;1 from tomato. Transport by LeAMT1;1 was affected by mutations that were predicted to constitute the aromatic recruitment site for NH 4} +} at the external pore entrance. Despite the structural similarities, LeAMT1;1 was shown to transport only the ion; each transported 14}C-MeA molecule carried a single, positive elementary charge. Similarly, NH 4} +} (or H +}/NH 3}) was transported, but NH 3} conduction was excluded. It is concluded that related proteins and a similar molecular architecture can apparently support contrasting transport mechanisms.

Mots clés: Life Sciences

Maria Mayer, Marek Dynowski, Uwe Ludewig. Ammonium ion transport by the AMT/Rh homolog LeAMT1;1. Biochemical Journal, 2006, 396 (3), pp.431-437. ⟨10.1042/BJ20060051⟩. ⟨hal-00478508⟩