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Published on: October 21, 2018
Microcin J25 membrane interaction: selectivity toward gel phase
Fernando Dupuy1, Roberto Morero
1Departamento Bioquímica de la Nutrición, INSIBIO-CONICET/UNT e Instituto de Química Biológica Dr. Bernabé Bloj, Universidad Nacional de Tucumán, Tucumán, Argentina.
Abstract:
The interaction of the tryptophan-containing variant of microcin J25, MccJ25 I13W, with phosphatidylcholine membranes was studied by fluorescence spectroscopy techniques. The peptide was able to interact with dimiristoylphophatidylcholine and dipalmitoylphosphatidylcholine liposomes only when the membranes were in gel phase, as was demonstrated by the blue shift of the intrinsic fluorescence of MccJ25 I13W. The binding isotherm showed a cooperative partition of the peptide toward the membrane and the binding constant increased as the temperature decreased and the order parameter increased. No interaction with liquid crystalline membranes was observed. Studies of dynamic quenching of the fluorescence indicated that the peptide penetrated the lipid bilayer and was located primarily in the interfacial region. Our results suggest that MccJ25 I13W interacts with gel phase phospholipids and increases both its own affinity for the bilayer and the membrane permeability of small ions.
Insights
The microcin J25 variant MccJ25 I13W peptide binds to gel-phase phosphatidylcholine membranes, not liquid-phase ones. This interaction enhances membrane permeability and peptide affinity for the lipid bilayer.
Area of Science:
- Biochemistry
- Membrane Biophysics
- Peptide-Lipid Interactions
Background:
- Microcin J25 (MccJ25) is a cyclic peptide antibiotic.
- Understanding peptide-membrane interactions is crucial for drug development.
- The MccJ25 I13W variant offers a unique model for studying these interactions.
Purpose of the Study:
- To investigate the interaction of MccJ25 I13W with phosphatidylcholine membranes.
- To determine the phase preference and binding characteristics of MccJ25 I13W.
- To elucidate the location and effects of MccJ25 I13W within lipid bilayers.
Main Methods:
- Fluorescence spectroscopy
- Dynamic quenching studies
- Liposome preparation (DMPC, DPPC)
Main Results:
- MccJ25 I13W selectively binds to gel-phase phosphatidylcholine membranes.
- Binding affinity increases with decreased temperature and increased membrane order.
- The peptide partitions cooperatively and localizes to the interfacial region of the bilayer.
- No interaction observed with liquid crystalline membranes.
- Increased membrane permeability to small ions was observed.
Conclusions:
- MccJ25 I13W exhibits specific binding to gel-phase phospholipids.
- The peptide insertion into the lipid bilayer is temperature-dependent.
- MccJ25 I13W enhances both its own affinity and membrane permeability.
