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Water movement during channel opening and closing
Journal of Bioenergetics and Biomembranes
|August 1, 1987
Summary
The voltage-dependent anion channel (VDAC) undergoes significant structural changes and water movement during gating, not just simple constriction. This suggests hydration plays a key role in channel function.
Area of Science:
- Biophysics
- Molecular Biology
- Membrane Transport
Background:
- Voltage-gated ion channels control cellular electrical activity.
- The gating mechanism of the voltage-dependent anion channel (VDAC) is not fully understood.
- Previous estimates of VDAC channel volume relied on indirect methods.
Purpose of the Study:
- To measure the polymer-inaccessible internal water volume change (delta nu) in VDAC.
- To elucidate the structural rearrangements during VDAC channel gating.
- To investigate the role of water and hydration in VDAC function.
Main Methods:
- Applied osmotic stress using a non-penetrating polymer.
- Measured the change in polymer-inaccessible internal water volume (delta nu).
- Compared delta nu with VDAC volume estimates from solute penetrability, conductance, and imaging.
Main Results:
- VDAC gating resulted in a delta nu comparable to its total estimated channel volume.
- This indicates substantial structural reorganization and water movement during gating.
- The observed changes are much larger than predicted by simple constriction models.
Conclusions:
- VDAC gating involves significant structural changes and water displacement, not just local blockade.
- Internal channel surface hydration is likely a critical factor in VDAC gating.
- Hydration dynamics may generally influence macromolecular interactions and channel function.