Stopped‐Flow Fluorimetry Using Voltage‐Sensitive Fluorescent Membrane Probes

Electrical techniques play a central role among the various methods for functional characterization of membrane transport proteins. Standard electrophysiological methods, that is, voltage-clamp and patch-clamp techniques, are especially useful in the analysis of ion channels. Based on the combination of structural and functional analyses of bacterial transporters, principles of the mechanism of transporters in general are emerging. The solid-supported membranes (SSM) represent a convenient model system for a lipid bilayer membrane with the advantage of being mechanically so stable that solutions can be rapidly exchanged at the surface. P-type ATPases are a large and varied family of membrane transporters that are of fundamental importance in virtually all living organisms. This chapter focuses on how the SSM-based electrophysiology has contributed to unraveling the transport mechanism of two prominent members of the P-type ATPase family, that is, the sarcoplasmic reticulum Ca²⁺ -ATPase and the human Cu⁺-ATPase (ATP7A and ATP7B)