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. 2002 Feb;82(2):908–914. doi: 10.1016/S0006-3495(02)75452-0

Sigmoidal concentration dependence of antimicrobial peptide activities: a case study on alamethicin.

Fang-Yu Chen 1, Ming-Tao Lee 1, Huey W Huang 1
PMCID: PMC1301899  PMID: 11806932

Abstract

The transition of the state of alamethicin from its inactive state to its active state of pore formation was measured as a function of the peptide concentration in three different membrane conditions. In each case the fraction of the alamethicin molecules occupying the active state, phi, showed a sigmoidal concentration dependence that is typical of the activities of antimicrobial peptides. Such a concentration dependence is often interpreted as due to peptide aggregation. However, we will show that a simple effect of aggregation cannot explain the data. We will introduce a model based on the elasticity of membrane, taking into consideration the membrane-thinning effect due to protein inclusion. The elastic energy of membrane provides an additional driving force for aggregation. The model produces a relation that not only predicts the correct concentration dependence but also explains qualitatively how the dependence changes with membrane conditions. The result shows that the membrane-mediated interactions between monomers and aggregates are essential for the strong cooperativity shown in pore formation.

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Selected References

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