An introduction to the methods available for ion channel reconstitution

Reconstitution describes the disassembly of a complex structure; the isolation of one or more of the components of that system and the reassembly of these components into an intelligible, measurable system. When applied to membrane proteins, such as ion-channels, it describes the solubilisation of the membrane, the isolation of the channel protein from the other membrane constituents and the reintroduction of that protein into some form of artificial membrane system which facilitates the measurement of channel function. However, in practice, the term is often applied less rigorously in the study of ion channel function and can be used to describe the incorporation of intact membrane vesicles, including the protein of interest, into artificial membrane systems that allow the properties of the channel to be investigated. In this chapter I will describe methods that are currently in use for incorporation of both native and purified channel proteins into artificial membranes. The diversity of the subject means that the technical aspects of the various approaches cannot be covered in detail; rather, this chapter is designed to act as an introduction to ion channel reconstitution. Detailed descriptions of experimental protocols can be obtained from the literature cited throughout the chapter. Ion-channel function can be monitored in a number of ways; by monitoring isotope flux in isolated tissues or membrane vesicles, or by using electrophysiological techniques, such as whole cell voltage-clamp or patch-clamp. What then are the advantages of monitoring channel function following incorporation into some form of artificial membrane?