title: Structural and mechanistic aspects of Amt/Rh proteins.
abstract: Amt/Rh proteins, which mediate movement of ammonium across cell membranes, are spread throughout the three kingdoms of life. Most functional studies on various members of the family have been performed using cellular assays in heterologous expression systems, which are, however, not very well suited for detailed mechanistic studies. Although now generally considered to be ammonia conducting channels, based on a number of experimental studies and structural insights, the possibility remains that some plant Amts facilitate net ammonium ion transport. The Escherichia coli channel AmtB has become the model system of choice for analysis of the mechanism of ammonia conductance, increasingly also through molecular dynamics simulations. Further progress in a more detailed mechanistic understanding of these proteins requires a reliable in vitro assay using purified protein, allowing quantitative kinetic measurements under a variety of experimental conditions for different Amt/Rh proteins, including mutants. Here, we critically review the existing functional data in the context of the most interesting and unresolved mechanistic questions and we present our results, obtained using an in vitro assay set up with the purified E. coli channel AmtB.
authors: Biomolecular Research, Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
authors: Arnaud
authors: A
authors: Javelle
authors: Domenico
authors: D
authors: Lupo
authors: Xiao-Dan
authors: XD
authors: Li
authors: Mike
authors: M
authors: Merrick
authors: Mohamed
authors: M
authors: Chami
authors: Pierre
authors: P
authors: Ripoche
authors: Fritz K
authors: FK
authors: Winkler
mesh_terms: D000818:Animals; D001681:Biological Assay; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000648:ultrastructure; D008954:Models, Biological; D011487:Protein Conformation; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*
chemical_list: C111096:AmtB protein, E coli; D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; D008562:Membrane Glycoproteins; D000644:Quaternary Ammonium Compounds