Figure 2.

Bax permeabilizes liposomal membranes when liposomes pre-incubated with tBid are also present. (a) Principle of the protein transfer experiment: liposomes pre-incubated with tBid (black ovals) and encapsulating one type of fluorophore (red – color arbitrary) are mixed with liposomes not pre-incubated with tBid and filled with a spectrally different fluorophore (blue – color arbitrary). Liposome permeabilization on the addition of Bax can then be monitored separately. (b) Permeabilization of a 1 : 1 ratio of liposomes either pre-incubated with 20 nM tBid (filled symbols) or not (empty symbols) when mixed together and incubated with 100 nM Bax. Data represented by the same color symbols were recorded simultaneously in the same solution, using spectrally different encapsulated fluorophores (ANTS and Tb) as shown in a. (c) Permeabilization of liposomes either pre-incubated with tBid or mixed with an equal amount of liposomes not pre-incubated with tBid (filled symbols) or vice versa (empty symbols) when incubated with the indicated amount of Bax. Curves with the same color have been recorded for the same Bax concentration but in two different solutions (one set of representative data). In b and c, lines represent exponential fits of the data. (d) Permeabilization half-time as a function of Bax concentration and (e) percentage of permeabilized liposomes after 3 h of incubation (mean±S.E.M., n=3). The fit of the data with either a power law (d) or a sigmoidal function (e) is shown for both liposome populations