Measuring pore formation by Bcl-2 family proteins

Two methods for assaying Bcl-2 protein family-induced solute efflux from liposomes have been outlined. They utilize either ion-selective electrodes to follow ion efflux or fluorescence to monitor changes in fluorescence of the liposome-encapsulated dye SPQ or carboxyfluorescein. Both methods provide a simple means of determining protein activity. These methods do not have the capability to detect either single-channel conductivity or ion selectivity, but they indicate whether the bulk of the protein population is inducing solute efflux. Although in in vivo significance of Bcl-2 protein family pore formation remains to be determined, in vitro measurements of channel activity should provide a means to determine whether a given protein preparation has activity and whether mutations have an adverse effect on channel formation.