Site of fluorescent label modifies interaction of melittin with live cells and model membranes

https://doi.org/10.1016/j.bbamem.2015.06.004Get rights and content
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Highlights

  • Effect of melittin on vesicles and live cells was studied by fluorescence microscopy.

  • Changes in morphology of HeLa cells and bleb formation in plasma membranes occurred.

  • Membrane disruptive effect was dependent upon the location of the fluorescent label.

  • Proline at position 14 appeared to be important for bioactivity of melittin.

Abstract

The mechanism of membrane disruption by melittin (MLT) of giant unilamellar vesicles (GUVs) and live cells was studied using fluorescence microscopy and two fluorescent synthetic analogues of MLT. The N-terminus of one of these was acylated with thiopropionic acid to enable labeling with maleimido-AlexaFluor 430 to study the interaction of MLT with live cells. It was compared with a second analogue labeled at P14C. The results indicated that the fluorescent peptides adhered to the membrane bilayer of phosphatidylcholine GUVs and inserted into the plasma membrane of HeLa cells. Fluorescence and light microscopy revealed changes in cell morphology after exposure to MLT peptides and showed bleb formation in the plasma membrane of HeLa cells. However, the membrane disruptive effect was dependent upon the location of the fluorescent label on the peptide and was greater when MLT was labeled at the N-terminus. Proline at position 14 appeared to be important for antimicrobial activity, hemolysis and cytotoxicity, but not essential for cell membrane disruption.

Keywords

Melittin
Cytotoxicity
Hemolysis
Microscopy
Fluorescence
Cell membranes

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