Assessing water permeability of aquaporins in a proteoliposome-based stopped-flow setup

Aquaporins (AQPs) are water channels embedded in the cell membrane that are crit-ical in maintaining water homeostasis. We describe a protocol for determining the water permeation capacity of AQPs reconstituted into proteoliposomes. Using a stopped-flow setup, AQP embedded in proteoliposomes are exposed to an osmo-genic gradient that triggers water flux. The consequent effects on proteoliposome size can be tracked using the fluorescence of an internalized fluorophore. This en-ables controlled characterization of water flux by AQPs. For complete details on the use and execution of this protocol, please refer to Kitchen et al. (2020).

Automated summary

AQPs, as critical water channels, play an important role in maintaining water homeostasis. This protocol describes a method to determine the water permeation capacity of AQPs by tracking the change in proteoliposome size exposed to an osmogenic gradient.