Incorporation kinetics in a membrane, studied with the pore-forming peptide alamethicin.
The reaction of fluorescence-labeled alamethicin with unilamellar phospholipid vesicles (DOPC and DMPC) has been investigated in a stopped-flow apparatus. Clearly single exponential time functions have been observed at temperatures above the phase transition of the bilayer. This can be interpreted in terms of an essentially one-step incorporation process. The pseudo first-order forward rate is found to be quite fast, falling in a range somewhat below the diffusion controlled upper bound. The data are quantitatively very well described on the basis of a simple mechanism. This comprises diffusion of peptide into the bilayer accompanied by a more or less slower change of the secondary structure. Aggregation of the incorporated molecules at higher concentrations is indicated to be comparatively rapid.
Department of Biophysical Chemistry, Biocenter of the University, Basel, Switzerland.
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G
Schwarz
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Gerke
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Rizzo
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Stankowski
D000408:Alamethicin; D000900:Anti-Bacterial Agents; D004134:Dimyristoylphosphatidylcholine; D007700:Kinetics; D008051:Lipid Bilayers; D008954:Models, Biological; D010713:Phosphatidylcholines
D000900:Anti-Bacterial Agents; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D000408:Alamethicin; C017251:1,2-oleoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine