Mechanism of ammonia transport by Amt/MEP/Rh: structure of AmtB at 1.35 AKhademi, S., O'Connell III, J., Remis, J., Robles-Colmenares, Y., Miercke, L.J.W., Stroud, R.M.
(2004) Science 305: 1587-1594
- PubMed: 15361618
- DOI: https://doi.org/10.1126/science.1101952
- Primary Citation of Related Structures:
1U77, 1U7C, 1U7G
- PubMed 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.
Department of Biochemistry and Biophysics, S412C Genentech Hall, University of California-San Francisco, 600 16th Street, San Francisco, CA 94143-2240, USA.