Visualization of a water-selective pore by electron crystallography in vitreous ice.
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.
Ren
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Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Reddy
V S
VS
Cheng
A
A
Melnyk
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P
Mitra
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AK
D000595:Amino Acid Sequence; D051398:Aquaporin 1; D020346:Aquaporins / Q000737:chemistry*; D003461:Crystallography; D004583:Electrons; D007053:Ice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D014867:Water / Q000737:chemistry
D020346:Aquaporins; D007053:Ice; D014867:Water; D051398:Aquaporin 1