Methodologies to Study Channel-Mediated Ion Fluxes in Membrane Vesicles

Abstract

The use of techniques such as voltage clamp or patch clamp has provided a great deal of information about channel properties and about ion movement across ion channels in biological membranes. However, neither of these techniques can be used to study the presence and properties of ion channels in very small cells or in internal membranes such as the sarcoplasmic reticulum of skeletal muscle. A clever technique developed by Miller and Racker (1976) has made it possible to overcome these problems: the membrane of interest, once isolated and purified, is allowed to fuse to an artificial planar lipid bilayer under appropriate conditions. Thus, ion channels and probably other membrane components are incorporated into the artificial membrane (for a review on the technique, see Miller, 1983a,b). Using this approach, various channels have been studied, including a voltage-gated K+ channel from sarcoplasmic reticulum (Miller, 1978), a Cl- channel from Torpedo electroplax (White and Miller, 1979), and a Ca2+-activated K+ channel from skeletal muscle transverse tubule (Latorre et al., 1982). None of these channels was known to exist before these experiments were done.