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Ion gradient-induced membrane translocation of model peptides
A I de Kroon1, B Vogt, R van't Hof
1Centre for Biomembranes and Lipid Enzymology, University of Utrecht, The Netherlands.
Biophysical Journal
|September 1, 1991
Summary
Synthetic peptides accumulate inside vesicles due to a K+ diffusion potential. This peptide uptake is primarily driven by the pH gradient, indicating translocation of the neutral peptide form across the membrane.
Area of Science:
- Biochemistry
- Biophysics
- Membrane Biology
Background:
- Synthetic peptides can associate with lipid bilayers.
- K+ diffusion potentials influence peptide-vesicle interactions.
Purpose of the Study:
- To determine the precise localization of positively charged synthetic peptides within large unilamellar vesicles (LUVs).
- To elucidate the roles of membrane potential (delta psi) and pH gradient (delta pH) in peptide accumulation.
Main Methods:
- Fluorescence measurements using tryptophan as an intrinsic probe.
- Utilizing vesicles with asymmetric transbilayer distribution of brominated phosphatidylcholine (PC) as a fluorescence quencher.
- Assessing pH and delta pH dependencies of peptide accumulation.
Main Results:
- The positively charged peptide (AIXme+) accumulates in the inner leaflet of the vesicle membrane under a K+ diffusion potential (negative inside).
- Peptide accumulation is predominantly governed by the transbilayer pH gradient (acidic inside), suggesting translocation of the neutral peptide form.
- Incorporation of cardiolipin (CL) did not significantly affect AIXme+ uptake, but influenced the response of a dicationic peptide (RXme2+).
Conclusions:
- K+ diffusion potential-induced peptide accumulation in LUVs is mainly driven by the pH gradient, facilitating neutral peptide translocation.
- The findings provide insights into the mechanisms of peptide-membrane interactions and transport across lipid bilayers.