Editors' ChoiceStructural Biology

Ensuring Adequate Gas Supplies

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Science's STKE  14 Sep 2004:
Vol. 2004, Issue 250, pp. tw330
DOI: 10.1126/stke.2502004tw330

In an uncertain world, survival may depend on leaving nothing to chance. In biochemical terms, the way to place a spontaneously occurring process under control is to make an enzyme that catalyzes the reaction. Biological membranes are inherently permeable to gases, such as oxygen, yet Khademi et al. (see the cover and the Perspective by Knepper and Agre) now describe a bacterial protein that functions as an ammonia channel. The crystal structure of AmtB reveals a vestibule where the water-soluble species NH4+ is deprotonated and a hydrophobic conduit enables NH3 to cross the membrane. The human analog of AmtB is the well-known rhesus or Rh factor.

S. Khademi, J. O'Connell III, J. Remis, Y. Robles-Colmenares, L. J. W. Miercke, R. M. Stroud, Mechanism of ammonia transport by Amt/MEP/Rh: Structure of AmtB at 1.35 Å. Science 305, 1587-1594 (2004). [Abstract] [Full Text]

M. A. Knepper, P. Agre, The atomic architecture of a gas channel. Science 305, 1573-1574 (2004). [Summary] [Full Text]

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