Peptides derived from apoptotic Bax and Bid reproduce the poration activity of the parent full-length proteins.
Bax and Bid are proapoptotic proteins of the Bcl-2 family that regulate the release of apoptogenic factors from mitochondria. Although they localize constitutively in the cytoplasm, their apoptotic function is exerted at the mitochondrial outer membrane, and is related to their ability to form transbilayer pores. Here we report the poration activity of fragments from these two proteins, containing the first alpha-helix of a colicinlike hydrophobic hairpin (alpha-helix 5 of Bax and alpha-helix 6 of Bid). Both peptides readily bind to synthetic lipid vesicles, where they adopt predominantly alpha-helical structures and induce the release of entrapped calcein. In planar lipid membranes they form ion conducting channels, which in the case of the Bax-derived peptide are characterized by a two-stage pattern, a large conductivity and lipid-charge-dependent ionic selectivity. These features, together with the influence of intrinsic lipid curvature on the poration activity and the existence of two helical stretches of different orientations for the membrane-bound peptide, suggest that it forms mixed lipidic/peptidic pores of toroidal structure. In contrast, the assayed Bid fragment shows a markedly different behavior, characterized by the formation of discrete, steplike channels in planar lipid bilayers, as expected for a peptidic pore lined by a bundle of helices.
García-Sáez
Ana J
AJ
Department of Biochemistry and Molecular Biology, University of Valencia, Burjassot, Spain.
Coraiola
Manuela
M
Dalla Serra
Mauro
M
Mingarro
Ismael
I
Menestrina
Gianfranco
G
Salgado
Jesús
J
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein; D055592:Biophysical Phenomena; D001703:Biophysics; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008081:Liposomes; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010539:Permeability; D017433:Protein Structure, Secondary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D007473:Ion Channels; D008081:Liposomes; D046912:Multiprotein Complexes; D010446:Peptide Fragments; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein