Daptomycin–Phosphatidylglycerol Domains in Lipid Membranes
Year: 2017
Type: article
Abstract: Daptomycin is an acidic, 13-amino acid, cyclic polypeptide that contains a number of nonproteinogenic residues and is modified at its N-terminus with a decanoyl chain. It has been in clinical use since 2003 against selected drug-resistant Staphylococcus aureus and Enterococcus spp infections. In vitro, daptomycin is active against Gram-positive pathogens at low concentrations but its antibiotic activity depends critically on the presence of calcium ions. This dependence has been thought to arise from binding of one or two Ca 2+ ions to daptomycin as a required step in its interaction with the bacterial membrane. Here, we investigated the interaction of daptomycin with giant unilamellar vesicles (GUVs) composed 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and 1-palmitoyl-2-oleoylphosphatidylglycerol (POPG). We used fluorescence confocal microscopy to monitor binding of the peptide to GUVs and follow its effect on the membrane of the vesicle. We found that in the absence of POPG or Ca 2+ daptomycin does not bind measurably to the lipid membrane. In the presence of 20–30% PG in the membrane and 2 mM Ca 2+, daptomycin induces the formation of membrane domains rich in acidic lipids. This effect is not induced by Ca 2+ alone. In addition, daptomycin causes GUV collapse, but it does not translocate across the membrane to the inside of intact POPC/POPG vesicles. We conclude that pore formation is probably not the mechanism by which the peptide functions. On the other hand, we found that daptomycin coclusters with the anionic phospholipid POPG and the fluorescent probes used, leading to extensive formation of daptomycin–POPG domains in the membrane.
Source: Langmuir
Institution: University of North Carolina Wilmington
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2767984528