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Structural basis of membrane-induced cardiotoxin A3 oligomerization
Farhad Forouhar1, Wei-Ning Huang, Jyung-Hurng Liu
1Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan 115.
The Journal of Biological Chemistry
|March 28, 2003
Summary
Cobra cardiotoxins (CTXs) interacting with anionic lipids cause dimerization, a key step for membrane fusion and pore formation. Crystal structures reveal how SDS stabilizes these CTX dimers, mimicking lipid interactions.
Area of Science:
- Biochemistry
- Structural Biology
- Membrane Biophysics
Background:
- Cobra cardiotoxins (CTXs) induce membrane fusion and pore formation in lipid bilayers.
- Anionic lipids like phosphatidylserine are crucial for these CTX-membrane interactions.
Purpose of the Study:
- To investigate the role of CTX dimerization in lipid-induced membrane fusion and pore formation.
- To elucidate the structural basis of CTX oligomerization mediated by anionic lipids.
Main Methods:
- X-ray crystallography of CTX A3 complexed with SDS at 1.9-Å resolution.
- Analysis of crystal packing to identify CTX dimer structures (D1 and D2) and stabilizing SDS molecules.
- Comparison of crystal structure data with NMR and Fourier transform infrared spectroscopy results from model membranes.
Main Results:
- CTX interaction with negatively charged lipids promotes CTX dimerization, an intermediate for oligomerization.
- Crystal structure of CTX A3-SDS complex reveals two types of CTX dimers (D1, D2) stabilized by SDS molecules.
- The orientation of CTX A3 monomers relative to SDS in the crystal mimics their orientation with model membranes.
Conclusions:
- Lipid-induced CTX dimerization is a critical step for forming membrane fusion intermediates (inverted micelles) and membrane pores.
- The crystal structure provides insights into the mechanism of CTX oligomerization at the molecular level.
- SDS can serve as a valuable tool in X-ray diffraction studies of protein-membrane interactions.