PMID:15361618
| Citation |
Khademi, S, O'Connell, J 3rd, Remis, J, Robles-Colmenares, Y, Miercke, LJ and Stroud, RM (2004) Mechanism of ammonia transport by Amt/MEP/Rh: structure of AmtB at 1.35 A. Science 305:1587-94 |
|---|---|
| Abstract |
The first structure of an ammonia channel from the Amt/MEP/Rh protein superfamily, determined to 1.35 angstrom resolution, shows it to be a channel that spans the membrane 11 times. Two structurally similar halves span the membrane with opposite polarity. Structures with and without ammonia or methyl ammonia show a vestibule that recruits NH4+/NH3, a binding site for NH4+, and a 20 angstrom-long hydrophobic channel that lowers the NH4+ pKa to below 6 and conducts NH3. Favorable interactions for NH3 are seen within the channel and use conserved histidines. Reconstitution of AmtB into vesicles shows that AmtB conducts uncharged NH3. |
| Links |
PubMed Online version:10.1126/science.1101952 |
| Keywords |
Amino Acid Sequence; Ammonia/metabolism; Binding Sites; Biological Transport; Cation Transport Proteins/chemistry; Cation Transport Proteins/genetics; Cation Transport Proteins/metabolism; Cell Membrane/chemistry; Crystallization; Crystallography, X-Ray; Escherichia coli/chemistry; Escherichia coli/metabolism; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Hydrogen Bonding; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Liposomes; Membrane Potentials; Models, Molecular; Molecular Sequence Data; Protein Conformation; Protein Folding; Protein Structure, Quaternary; Protein Structure, Secondary; Quaternary Ammonium Compounds/metabolism; Rh-Hr Blood-Group System/chemistry; Rh-Hr Blood-Group System/metabolism; Sequence Alignment; Water/chemistry; Water/metabolism |
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