TY - JOUR
T1 - Surface aggregation and membrane penetration by peptides
T2 - Relation to pore formation and fusion
AU - Nir, Shlomo
AU - Nicol, Francois
AU - Szoka, Francis C.
PY - 1999
Y1 - 1999
N2 - The peptide GALA undergoes a conformational change to an amphipathic α-helix when the pH is reduced, inducing leakage of contents from vesicles. Leakage from neutral or negatively-charged vesicles at pH 5.0 was similar and could be adequately explained by a mathematical model which assumed that GALA becomes incorporated into the vesicle bilayer and irreversibly aggregates to form a pore consisting of M = 10 ± 2 peptides. Increasing cholesterol content in the membranes resulted in reduced leakage, and increased reversibility of surface aggregation of the peptide. Employing fluorescently labelled peptides confirmed that the degree of reversibility of surface aggregation of GALA was significantly larger in cholesterol containing liposomes. Orientation of the peptide GALA in bilayers was determined by a bodipy-avidin/biotin binding assay. The peptide was labelled by biotin at the N- or C-terminus and bodipy-avidin molecules were added externally or were preencapsulated in the vesicles. The peptides are arranged in the pore perpendicularly to the membrane, such that 3/4 of the N-termini are on the internal side of the membrane. The pores are stable and persist for at least 10 min. When the peptides form an aggregate of size smaller than M, the orientation of the peptide is mostly parallel to the surface and the biotinylated peptide does not translocate. When a critical size of the aggregate is attained, a rearrangement of the peptide occurs, which amounts to rapid penetration and formation of a pore structure. Induction of fusion by peptides may be antagonistic to pore formation, the outcome being dependent on vesicle aggregation.
AB - The peptide GALA undergoes a conformational change to an amphipathic α-helix when the pH is reduced, inducing leakage of contents from vesicles. Leakage from neutral or negatively-charged vesicles at pH 5.0 was similar and could be adequately explained by a mathematical model which assumed that GALA becomes incorporated into the vesicle bilayer and irreversibly aggregates to form a pore consisting of M = 10 ± 2 peptides. Increasing cholesterol content in the membranes resulted in reduced leakage, and increased reversibility of surface aggregation of the peptide. Employing fluorescently labelled peptides confirmed that the degree of reversibility of surface aggregation of GALA was significantly larger in cholesterol containing liposomes. Orientation of the peptide GALA in bilayers was determined by a bodipy-avidin/biotin binding assay. The peptide was labelled by biotin at the N- or C-terminus and bodipy-avidin molecules were added externally or were preencapsulated in the vesicles. The peptides are arranged in the pore perpendicularly to the membrane, such that 3/4 of the N-termini are on the internal side of the membrane. The pores are stable and persist for at least 10 min. When the peptides form an aggregate of size smaller than M, the orientation of the peptide is mostly parallel to the surface and the biotinylated peptide does not translocate. When a critical size of the aggregate is attained, a rearrangement of the peptide occurs, which amounts to rapid penetration and formation of a pore structure. Induction of fusion by peptides may be antagonistic to pore formation, the outcome being dependent on vesicle aggregation.
KW - Fusion
KW - Leakage
KW - Peptide pores
KW - Peptide translocation
KW - Surface aggregation
UR - http://www.scopus.com/inward/record.url?scp=0032903686&partnerID=8YFLogxK
U2 - 10.1080/096876899294814
DO - 10.1080/096876899294814
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C2 - 10332743
AN - SCOPUS:0032903686
SN - 0968-7688
VL - 16
SP - 95
EP - 101
JO - Molecular Membrane Biology
JF - Molecular Membrane Biology
IS - 1
ER -