BAX and BCL-2 form channels in artificial membranes with distinct characteristics, including BAX forming mildly Cl- selective channels and BCL-2 forming mildly K+ selective channels.
BAX and BCL-2 form distinct ion channels in artificial membranes, suggesting their biochemical functions may involve pore activity at specific membrane sites.
The BCL-2 family of proteins is composed of both pro- and antiapoptotic regulators, although its most critical biochemical functions remain uncertain. The structural similarity between the BCL-X L monomer and several ion-pore-forming bacterial toxins has prompted electrophysiologic studies. Both BAX and BCL-2 insert into KCl-loaded vesicles in a pH-dependent fashion and demonstrate macroscopic ion efflux. Release is maximum at ≈pH 4.0 for both proteins; however, BAX demonstrates a broader pH range of activity. Both purified proteins also insert into planar lipid bilayers at pH 4.0. Single-channel recordings revealed a minimal channel conductance for BAX of 22 pS that evolved to channel currents with at least three subconductance levels. The final, apparently stable BAX channel had a conductance of 0.731 nS at pH 4.0 that changed to 0.329 nS when shifted to pH 7.0 but remained mildly Cl − selective and predominantly open. When BAX-incorporated lipid vesicles were fused to planar lipid bilayers at pH 7.0, a Cl − -selective ( P K / P Cl = 0.3) 1.5-nS channel displaying mild inward rectification was noted. In contrast, BCL-2 formed mildly K + -selective ( P K / P Cl = 3.9) channels with a most prominent initial conductance of 80 pS that increased to 1.90 nS. Fusion of BCL-2-incorporated lipid vesicles into planar bilayers at pH 7.0 also revealed mild K + selectivity ( P K / P Cl = 2.4) with a maximum conductance of 1.08 nS. BAX and BCL-2 each form channels in artificial membranes that have distinct characteristics including ion selectivity, conductance, voltage dependence, and rectification. Thus, one role of these molecules may include pore activity at selected membrane sites.
Schlesinger et al. (Tue,) conducted a other in Apoptosis / Ion channel characteristics. BAX protein vs. BCL-2 protein was evaluated on Ion channel characteristics (conductance, ion selectivity, voltage dependence, rectification). BAX and BCL-2 form channels in artificial membranes with distinct characteristics, including BAX forming mildly Cl- selective channels and BCL-2 forming mildly K+ selective channels.