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Updated: Apr 11, 2026
Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Published on: May 29, 2011
Site of fluorescent label modifies interaction of melittin with live cells and model membranes
Elaheh Jamasbi1, Giuseppe D Ciccotosto2, Julien Tailhades3
1School of Chemistry, Bio21 Institute, The University of Melbourne, VIC 3010, Australia.
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.
Insights
Melittin (MLT) disrupts cell membranes by inserting into them, with N-terminus labeling showing greater membrane disruption. Proline at position 14 is key for toxicity but not membrane disruption.
Area of Science:
- Biochemistry
- Cell Biology
- Biophysics
Background:
- Melittin (MLT) is a peptide known for its membrane-disrupting properties.
- Understanding MLT's interaction with biological membranes is crucial for its therapeutic applications.
- Previous studies have explored MLT's effects, but the precise mechanism of membrane disruption and the role of specific peptide regions require further investigation.
Purpose of the Study:
- To elucidate the mechanism of membrane disruption by melittin (MLT) in giant unilamellar vesicles (GUVs) and live cells.
- To investigate the influence of fluorescent label location on MLT's interaction with and disruption of cell membranes.
- To compare the effects of MLT labeled at the N-terminus versus proline at position 14 (P14C) on membrane integrity and cell morphology.
Main Methods:
- Utilized fluorescence microscopy and two fluorescent synthetic analogues of MLT.
- Synthesized MLT analogues, one labeled at the N-terminus with maleimido-AlexaFluor 430 and another labeled at P14C.
- Studied interactions with phosphatidylcholine GUVs and live HeLa cells, observing changes in cell morphology and membrane integrity.
Main Results:
- Fluorescent MLT analogues adhered to GUV membrane bilayers and inserted into the plasma membrane of HeLa cells.
- Exposure to MLT peptides induced changes in cell morphology, including bleb formation in HeLa cells.
- The membrane disruptive effect was dependent on label location, being greater when MLT was labeled at the N-terminus.
- Proline at position 14 was important for antimicrobial activity, hemolysis, and cytotoxicity, but not essential for cell membrane disruption.
Conclusions:
- Melittin (MLT) interacts with and inserts into cell membranes, leading to morphological changes and disruption.
- The N-terminus of MLT plays a significant role in its membrane disruptive capacity.
- While proline at position 14 is critical for MLT's cytotoxic and hemolytic effects, it is not essential for the peptide's ability to disrupt cell membranes.
