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Examining BCL-2 Family Function with Large Unilamellar Vesicles
Published on: October 5, 2012
Conformational Heterogeneity in the Activation Mechanism of Bax
C Ashley Barnes1, Pushpa Mishra1, James L Baber2
1Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
Bax is known for its pro-apoptotic role within the mitochondrial pathway of apoptosis. However, the mechanism for transitioning Bax from cytosolic to membrane-bound oligomer remains elusive. Previous nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) studies defined monomeric Bax as conformationally homogeneous. Yet it has recently been proposed that monomeric Bax exists in equilibrium with a minor state that is distinctly different from its NMR structure. Here, we revisited the structural analysis of Bax using methods uniquely suited for unveiling "invisible" states of proteins, namely, NMR paramagnetic relaxation enhancements and EPR double electron-electron resonance (DEER). Additionally we examined the effect of glycerol, the co-solvent of choice in DEER studies, on the structure of Bax using NMR chemical-shift perturbations and residual dipolar couplings. Based on our combined NMR and EPR results, Bax is a conformationally homogeneous protein prior to its activation.
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