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Updated: Jul 12, 2026

Sample Preparation using a Lipid Monolayer Method for Electron Crystallographic Studies
Published on: November 20, 2021
The structural basis of water permeation and proton exclusion in aquaporins
1Department of Biology, Brookhaven National Laboratory, Upton, New York 11973, USA. dax@bnl.gov
Abstract:
Aquaporins (AQPs) represent a ubiquitous class of integral membrane proteins that play critical roles in cellular osmoregulations in microbes, plants and mammals. AQPs primarily function as water-conducting channels, whereas members of a sub-class of AQPs, termed aquaglyceroporins, are permeable to small neutral solutes such as glycerol. While AQPs facilitate transmembrane permeation of water and/or small neutral solutes, they preclude the conduction of protons. Consequently, openings of AQP channels allow rapid water diffusion down an osmotic gradient without dissipating electrochemical potentials. Molecular structures of AQPs portray unique features that define the two central functions of AQP channels: effective water permeation and strict proton exclusion. This review describes AQP structures known to date and discusses the mechanisms underlying water permeation, proton exclusion and water permeability regulation.
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