Tweaking Polybia-MP1: How a Lysine-Histidine Swap Redefines Its Surface Properties.

Area of Science:

• Biochemistry
• Materials Science
• Biophysics

Background:

• Polybia-MP1 (MP1) possesses antimicrobial and anticancer properties.
• A need exists for improved selectivity towards acidic tumor microenvironments.
• HMP1 was designed as a histidine-substituted analog of MP1 to achieve pH-responsive behavior.

Purpose of the Study:

• To synthesize and characterize HMP1, a histidine-substituted analog of MP1.
• To investigate HMP1's pH-dependent interactions with lipid membranes.
• To evaluate HMP1's potential for targeted therapeutics and drug delivery.

Main Methods:

• HMP1 synthesized by replacing lysine with histidine residues in MP1.
• Characterization of surfactant properties and lipid monolayer interactions (DPPC) under varying pH and ionic strength.
• Langmuir monolayer experiments to assess peptide-induced morphological changes and lipid packing effects.

Main Results:

• HMP1 exhibited pH-dependent activity between pH 5.5 and 7.5.
• HMP1 induced significant lipid domain reorganization and preferentially interacted with cholesterol-enriched membranes.
• HMP1 demonstrated non-hemolytic properties and lower cytotoxicity compared to MP1.

Conclusions:

• Lysine-to-histidine substitution in HMP1 confers pH sensitivity.
• HMP1 selectively modulates membrane organization based on lipid composition, packing, pH, and ionic environment.
• HMP1 shows promise for targeted therapeutics and pH-responsive drug delivery systems.