Peptides corresponding to helices 5 and 6 of Bax can independently form large lipid pores.
Proteins of the B-cell lymphoma protein 2 (Bcl2) family are key regulators of the apoptotic cascade, controlling the release of apoptotic factors from the mitochondrial intermembrane space. A helical hairpin found in the core of water-soluble folds of these proteins has been reported to be the pore-forming domain. Here we show that peptides including any of the two alpha-helix fragments of the hairpin of Bcl2 associated protein X (Bax) can independently induce release of large labelled dextrans from synthetic lipid vesicles. The permeability promoted by these peptides is influenced by intrinsic monolayer curvature and accompanied by fast transbilayer redistribution of lipids, supporting a toroidal pore mechanism as in the case of the full-length protein. However, compared with the pores made by complete Bax, the pores made by the Bax peptides are smaller and do not need the concerted action of tBid. These data indicate that the sequences of both fragments of the hairpin contain the principal physicochemical requirements for pore formation, showing a parallel between the permeabilization mechanism of a complex regulated protein system, such as Bax, and the much simpler pore-forming antibiotic peptides.
Department of Biochemistry and Molecular Biology, University of Valencia, Spain.
Ana J
AJ
García-Sáez
Manuela
M
Coraiola
Mauro Dalla
MD
Serra
Ismael
I
Mingarro
Peter
P
Müller
Jesús
J
Salgado
D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008081:Liposomes; D051379:Mice; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010539:Permeability; D017433:Protein Structure, Secondary; D051028:bcl-2-Associated X Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
C494827:Bax protein, mouse; D008051:Lipid Bilayers; D008081:Liposomes; D010446:Peptide Fragments; D051028:bcl-2-Associated X Protein