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Non-proton ion release in purple membrane
R Tóth-Boconádi1, S G Taneva, L Keszthelyi
1Institute of Biophysics, Biological Research Center, Szeged, Hungary.
Biophysical Journal
|December 1, 1994
Summary
Conductivity changes in bacteriorhodopsin are not due to ion release. Immobilizing purple membrane prevents these changes, suggesting altered polarizability during the photocycle is responsible.
Area of Science:
- Biophysics
- Membrane protein function
- Photochemistry
Background:
- Bacteriorhodopsin in purple membrane exhibits large conductivity changes during its photocycle.
- Previous hypotheses attributed these changes to non-proton ion release.
Purpose of the Study:
- To investigate the mechanism behind conductivity changes in bacteriorhodopsin photocycling.
- To test the hypothesis of non-proton ion release versus alternative explanations.
Main Methods:
- Comparison of conductivity measurements in suspended versus immobilized purple membrane.
- Analysis of photocycle-dependent phenomena in different membrane states.
Main Results:
- Conductivity changes were absent when purple membrane was immobilized.
- The presence of conductivity changes correlated with membrane mobility.
Conclusions:
- The observed conductivity changes are likely not due to ion release.
- An alternative hypothesis proposes that changes in purple membrane polarizability during the photocycle explain the conductivity phenomena.