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Daptomycin forms cation- and size-selective pores in model membranes.
TianHua Zhang1, Jawad K Muraih2, Ben MacCormick3
1Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada.
Biochimica Et Biophysica Acta
|May 27, 2014
Summary
Daptomycin forms calcium-dependent pores in bacterial membranes. These pores are selective for cations like sodium and potassium, explaining how daptomycin depolarizes and kills Gram-positive bacteria.
Area of Science:
- Microbiology
- Biochemistry
- Pharmacology
Background:
- Daptomycin is a critical lipopeptide antibiotic for treating severe Gram-positive bacterial infections.
- Its mechanism involves calcium-dependent membrane binding and oligomerization, leading to bacterial cell death.
- Observed bacterial membrane depolarization suggests daptomycin forms pores.
Purpose of the Study:
- To characterize the permeability properties of daptomycin-induced pores using a liposome model.
- To elucidate the specific ion selectivity of these daptomycin pores.
Main Methods:
- Utilized a liposome model system to investigate daptomycin pore formation.
- Assessed the permeability of various ions, including cations and anions, through these pores.
Main Results:
- Daptomycin pores are selective for cations, with highest permeability for alkali metal ions (Na+, K+).
- Permeability is reduced for divalent cations (Mg++) and organic cations (choline, hexamethonium).
- Anions and zwitterions like cysteine are excluded from the pores.
Conclusions:
- The characterized daptomycin pores explain the observed bacterial membrane depolarization.
- Sodium influx through these selective cation pores is the primary driver of depolarization in vivo.
- Findings provide insight into the molecular mechanism of daptomycin's bactericidal activity.
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