The water-selective pathway through the aquaporin-1 membrane channel has been visualized by fitting an atomic model to a 3.7-A resolution three-dimensional density map. This map was determined by analyzing images and electron diffraction patterns of lipid-reconstituted two-dimensional crystals of aquaporin-1 preserved in vitrified buffer in the absence of any additive. The aqueous pathway is characterized by a size-selective pore that is approximately 4.0 +/- 0.5A in diameter, spans a length of approximately 18A, and bends by approximately 25 degrees as it traverses the bilayer. This narrow pore is connected by wide, funnel-shaped openings at the extracellular and cytoplasmic faces. The size-selective pore is outlined mostly by hydrophobic residues, resulting in a relatively inert pathway conducive to diffusion-limited water flow. The apex of the curved pore is close to the locations of the in-plane pseudo-2-fold symmetry axis that relates the N- and C-terminal halves and the conserved, functionally important N76 and N192 residues.

• PMID: 11171962
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Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, Non-P.H.S. | Research Support, U.S. Gov't, P.H.S.

Authors

Ren G, Reddy VS, Cheng A, Melnyk P, Mitra AK

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