Use of Xenopus Oocytes to Measure Ionic Selectivity of Pore-Forming Peptides and Ion Channels
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The Xenopus laevis
oocyte is a widely used system for heterologous expression of exogenous ion channel proteins (1, 2)
. Among other advantages, these easy to obtain, mechanically and electrically stable, large-sized cells enable 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 the use of additional electrodes (1–3) for injection of diverse
materials (Ca2+
chelators, peptides, chemicals, antibodies, proteic-partners, and so on) 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 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 with artificial bilayers, oocytes offer a real animal plasma membrane where
biophysical properties and toxicity can be studied in the same environment.