Oligomerization and insertion of antimicrobial peptide TP4 on bacterial membrane and membrane-mimicking surfactant...

Area of Science:

• Biochemistry
• Microbiology
• Immunology

Background:

• Antimicrobial peptides (AMPs) are crucial for innate immunity against microbes.
• The precise mechanisms of AMP action on bacterial membranes remain largely unknown.
• Understanding AMPs' membrane interactions is key to developing new antimicrobial strategies.

Purpose of the Study:

• To elucidate the action mechanism of TP4 peptides from Nile tilapia on bacterial membranes.
• To investigate the oligomerization and membrane insertion process of TP4 peptides.
• To provide a model for AMPs' interaction with bacterial membranes.

Main Methods:

• Observing TP4 peptide interaction with E. coli using SYTOX Green.
• Analyzing peptide aggregation using sarkosyl and trifluoroethanol.
• Characterizing peptide particle morphology and size using microscopy.

Main Results:

• TP4 peptides rapidly induced E. coli membrane permeability to SYTOX Green.
• Peptides formed small dots on bacterial cells, suggesting localized membrane interaction.
• TP4 peptides oligomerized into soluble or insoluble forms driven by hydrophobic interactions and influenced by surfactant concentration.
• Insoluble oligomers formed larger particles (0.1-20 μm) through hydrophobic aggregation.
• Peptide morphology and solubility were concentration-dependent on exogenous agents.

Conclusions:

• TP4 peptides oligomerize on or within the bacterial membrane.
• Hydrophobic interactions are critical for TP4 peptide binding and aggregation.
• This study presents direct evidence and a model for AMP oligomerization and insertion into bacterial membranes prior to potential cytosolic entry.