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The concentration-dependent membrane activity of cecropin A
L Silvestro1, K Gupta, J N Weiser
1Department of Pharmacology, Infectious Diseases Section, and Johnson Foundation for Molecular Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6084, USA.
Biochemistry
|September 23, 1997
Summary
Cecropin A kills bacteria by disrupting ion gradients across their membranes. This antimicrobial peptide
Area of Science:
- Biochemistry
- Microbiology
- Molecular Biology
Background:
- Cecropin A is a cationic antimicrobial peptide.
- Its mechanism of bacterial killing is not fully understood, but involves the cell membrane.
Purpose of the Study:
- To investigate the membrane activity of cecropin A.
- To determine how cecropin A alters membrane permeability in synthetic lipid vesicles and bacteria.
Main Methods:
- Examined cecropin A's effect on ion gradients and probe release in synthetic lipid vesicles.
- Assessed cecropin A's bactericidal activity and effect on cytoplasmic content release in Gram-negative bacteria.
Main Results:
- Cecropin A dissipated ion gradients at low concentrations and released probes at high concentrations in vesicles.
- Anionic lipids enhanced peptide binding and probe release; cholesterol inhibited probe release at high peptide concentrations.
- Cecropin A was bactericidal at ion gradient-dissipating concentrations, but required higher concentrations to release cytoplasmic contents.
Conclusions:
- Cecropin A kills bacteria primarily by dissipating transmembrane electrochemical ion gradients.
- The findings do not support theories linking antimicrobial activity to probe release or specific roles for cholesterol/anionic lipids in selectivity.