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.
Schwarz
G
G
Department of Biophysical Chemistry, Biocenter of the University, Basel, Switzerland.
Gerke
H
H
Rizzo
V
V
Stankowski
S
S
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