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Interaction of the full-length Bax protein with biomimetic mitochondrial liposomes:

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1016/j.bbamem.2011.10.007
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Affiliation
  1. National Research Council of Canada. NRC Canadian Neutron Beam Centre
FormatText, Article
SubjectApoptosis; Bcl-2 family protein; Bax; FCS; FIDA; SANS
Abstract
In response to apoptotic stimuli, the pro-apoptotic protein Bax inserts in the outer mitochondrial membrane, resulting in the formation of pores and the release of several mitochondrial components, and sealing the cell's fate. To study the binding of Bax to membranes, we used an in vitro system consisting of 50 nm diameter liposomes prepared with a lipid composition mimicking that of mitochondrial membranes in which recombinant purified full-length Bax was inserted via activation with purified tBid. We detected the association of the protein with the membrane using fluorescence fluctuation methods, and found that it could well be described by an equilibrium between soluble and membrane-bound Bax and that at a high protein-to-liposome ratio the binding seemed to saturate at about 15 Bax proteins per 50 nm diameter liposome. We then obtained structural data for samples in this saturated binding regime using small-angle neutron scattering under different contrast matching conditions. Utilizing a simple model to fit the neutron data, we observed that a significant amount of the protein mass protrudes above the membrane, in contrast to the conjecture that all of the membrane-associated Bax states are umbrella-like. Upon protein binding, we also observed a thinning of the lipid bilayer accompanied by an increase in liposome radius, an effect reminiscent of the action of antimicrobial peptides on membranes.
Publication date
In
  • Biochimica et Biophysica Acta (BBA)-Biomembranes 1818, no. 3 (15 October 2011): 384–401.
LanguageEnglish
Peer reviewedYes
NPARC number20140156
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Record identifier369da6ec-f5cb-4e00-b360-7eee36c710fc
Record created2012-06-14
Record modified2020-04-21
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