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Interaction of wasp venom mastoparan with biomembranes
T Katsu1, M Kuroko, T Morikawa
1Faculty of Pharmaceutical Sciences, Okayama University, Japan.
Abstract:
Mastoparan-induced changes in the K+ permeability of rat peritoneal mast cells, human erythrocytes, Staphylococcus aureus and Escherichia coli were examined. Mastoparan did not efficiently increase the K+ permeability of cells except for S. aureus. The release of membrane phospholipids was also observed from S. aureus cells in the concentration range of the permeability enhancement. Mastoparan stimulated histamine release from mast cells, independently of a small efflux of K+. Mastoparan became markedly effective to E. coli cells whose outer membrane structure was chemically disrupted beforehand, showing that the peptide can enhance the permeability of the cytoplasmic membranes of both Gram-positive and -negative bacteria. In experiments using liposomes, mastoparan increased the permeability of the liposomes composed of egg phosphatidylethanolamine and egg phosphatidylglycerol, which are the lipid constituents of the cytoplasmic membrane of E. coli cells, while it showed a weak activity to the liposomes composed of egg phosphatidylcholine and cholesterol. The latter result related closely to the fact that this peptide acted weakly on erythrocytes and mast cells in which acidic lipids constitute a minor portion. Mastoparan decreased the phase transition temperature of dipalmitoylphosphatidylglycerol liposomes, but it did not affect that of dipalmitoylphosphatidylcholine liposomes. These results indicate that mastoparan penetrated into membranes mainly containing acidic phospholipids and disrupted the membrane structure to increase the permeability. The action of the wasp venom mastoparan was compared with that of a bee venom melittin.
Insights
Mastoparan, a peptide from wasp venom, disrupts bacterial membranes by increasing permeability, especially in those with acidic phospholipids. It shows limited effects on human cells and mast cells, highlighting its selective action.
Area of Science:
- Biochemistry
- Membrane Biophysics
- Microbiology
Background:
- Mastoparan is a peptide toxin found in wasp venom.
- Its effects on cell membrane permeability are not fully understood.
- Understanding mastoparan's mechanism can inform antimicrobial strategies.
Purpose of the Study:
- To investigate how mastoparan affects the K+ permeability of various cell types.
- To determine the role of membrane lipid composition in mastoparan's activity.
- To compare mastoparan's action with melittin from bee venom.
Main Methods:
- Assessing K+ efflux from rat mast cells, human erythrocytes, Staphylococcus aureus, and Escherichia coli.
- Analyzing phospholipid release from S. aureus.
- Conducting experiments with liposomes composed of different lipids (phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, cholesterol).
- Measuring the phase transition temperature of liposomes.
Main Results:
- Mastoparan significantly increased K+ permeability in S. aureus and pre-treated E. coli, but not in intact human erythrocytes or rat mast cells.
- Phospholipid release from S. aureus correlated with increased permeability.
- Liposomes rich in acidic phospholipids (phosphatidylethanolamine, phosphatidylglycerol) showed increased permeability upon mastoparan treatment.
- Mastoparan decreased the phase transition temperature of dipalmitoylphosphatidylglycerol liposomes, indicating membrane disruption.
Conclusions:
- Mastoparan primarily disrupts cell membranes containing acidic phospholipids.
- Its mechanism involves penetrating these membranes and altering their structure to increase permeability.
- The peptide exhibits selective activity, being more effective against bacteria than mammalian cells.