Magainin 2 Revisited: A Test of the Quantitative Model for the All-or-None Permeabilization of Phospholipid Vesicles
Autor: | Paulo F. Almeida, Antje Pokorny, Sonia M. Gregory |
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Rok vydání: | 2009 |
Předmět: |
Kinetics
Biophysics Peptide Xenopus Proteins Magainins Fluorescence 03 medical and health sciences chemistry.chemical_compound Phosphatidylcholine Unilamellar Liposomes 030304 developmental biology Phosphatidylglycerol chemistry.chemical_classification 0303 health sciences Chromatography Vesicle 030302 biochemistry & molecular biology Magainin Membrane Phosphatidylglycerols Fluoresceins Cecropin chemistry Models Chemical Phosphatidylcholines Algorithms Antimicrobial Cationic Peptides Protein Binding |
Zdroj: | Biophysical Journal. 96(1):116-131 |
ISSN: | 0006-3495 |
DOI: | 10.1016/j.bpj.2008.09.017 |
Popis: | The all-or-none kinetic model that we recently proposed for the antimicrobial peptide cecropin A is tested here for magainin 2. In mixtures of phosphatidylcholine (PC)/phosphatidylglycerol (PG) 50:50 and 70:30, release of contents from lipid vesicles occurs in an all-or-none fashion and the differences between PC/PG 50:50 and 70:30 can be ascribed mainly to differences in binding, which was determined independently and is approximately 20 times greater to PC/PG 50:50 than to 70:30. Only one variable parameter, beta, corresponding to the ratio of the rates of pore opening to pore closing, is used to fit dye release kinetics from these two mixtures, for several peptide/lipid ratios ranging from 1:25 to 1:200. However, unlike for cecropin A where it stays almost constant, beta increases five times as the PG content of the vesicles increases from 30 to 50%. Thus, magainin 2 is more sensitive to anionic lipid content than cecropin A. But overall, magainin follows the same all-or-none kinetic model as cecropin A in these lipid mixtures, with slightly different parameter values. When the PG content is reduced to 20 mol %, dye release becomes very low; the mechanism appears to change, and is consistent with a graded kinetic model. We suggest that the peptide may be inducing formation of PG domains. In either mechanism, no peptide oligomerization occurs and magainin catalyzes dye release in proportion to its concentration on the membrane in a peptide state that we call a pore. We envision this structure as a chaotic or stochastic type of pore, involving both lipids and peptides, not a well-defined, peptide-lined channel. |
Databáze: | OpenAIRE |
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