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Characterization of Multi-subunit Protein Complexes of Human MxA Using Non-denaturing Polyacrylamide Gel-electrophoresis
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Oligomerization process of Bcl-2 associated X protein revealed from intermediate structures in solution
Orion Shih1, Yi-Qi Yeh1, Kuei-Fen Liao1
1National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan. usjeng@nsrrc.org.tw.
Physical Chemistry Chemical Physics : PCCP
|March 7, 2017
Summary
This study reveals the intermediate structures of BCL2-associated X (BAX) protein during apoptosis. It suggests a ditopic oligomerization mechanism involving extended dimers, clarifying the pathway to cell death.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- The BCL2-associated X (BAX) protein initiates apoptosis by permeabilizing mitochondrial membranes.
- While BAX oligomers are studied, the intermediate structures in its activation pathway remain unclear.
Purpose of the Study:
- To characterize the intermediate structures of BAX during its oligomerization.
- To elucidate the mechanism of BAX-mediated mitochondrial outer membrane permeabilization.
Main Methods:
- Combined small-angle X-ray scattering (SAXS) with on-line gel-filtration.
- Electron spin resonance (ESR) spectroscopy.
- Molecular dynamics simulations.
Main Results:
- Identified BAX monomers, dimers, and tetramers as key intermediates.
- Reconstructed intermediate structures using integrated SAXS and ESR data.
- Revealed a ditopic oligomerization mechanism involving extended dimers with protruding α6 chains.
Conclusions:
- Proposed a linear oligomerization pathway for BAX.
- The ditopic dimer conformation facilitates winding into helical rod structures.
- This mechanism bridges solution intermediates to large BAX assemblies on mitochondria.
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