Ion Selectivity of Pore-Forming Peptides and Ion Channels Measured in Xenopus Oocytes
The Xenopus laevis oocyte is a widely used system for heterologous expression of exogenous ion channel proteins. They are easy to obtain, mechanically and electrically stable, have a large size, enabling multiple types of electrophysiological recordings: two-electrode voltage clamp, single cell-attached or cell-free patch-clamp and macropatch recordings. The size of an oocyte (1 mm in diameter) also allows for the use of additional electrodes (from 1 to 3) for injection of diverse materials (Ca2+ chelators, peptides, chemicals, antibodies, proteic-partners, etc.) before or during the course of the electrophysiological experiment.
We have successfully used this system to analyze the biophysical properties of pore-forming peptides. Simple extracellular perfusion of these peptides induced the formation of channels in the oocyte plasma membrane; these channels can then be studied and characterized in diverse ionic conditions. The ease of the perfusion and the stability of the voltage-clamped oocyte make it a powerful tool for such analyses. Compared to artificial bilayers, oocytes offer a real animal plasma membrane where biophysical properties and toxicity can be studied in the stable environment.
Key wordsVoltage clamp Reversal potential Calcium channels Anomalous mole fraction
This work was supported by CNRS, INSERM, and ANR. The authors would like to thank Dr. I. Lefevre for critical reading of the manuscript and Jean-Marc Donnay for oocyte preparation.
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