Membrane-damaging activity of Taiwan cobra cardiotoxin 3 is responsible for its bactericidal activity

Area of Science:

• Biochemistry
• Microbiology
• Toxicology

Background:

• Cardiotoxins (CTX) from Naja naja atra are known for their potent biological activities.
• Understanding the mechanism of CTX antibacterial action is crucial for developing novel antimicrobial agents.

Purpose of the Study:

• To investigate the causal relationship between membrane-damaging activity and bactericidal activity of Naja naja atra cardiotoxin 3 (CTX3).
• To elucidate the role of membrane permeability and bacterial cell wall components in CTX3's antibacterial efficacy.

Main Methods:

• Bacterial growth inhibition assays for Staphylococcus aureus and Escherichia coli.
• Membrane permeability assays using model membranes.
• Morphological examination of bacterial cells.
• Analysis of CTX3 binding to lipopolysaccharide (LPS) and lipoteichoic acid (LTA).
• Assessment of CTX3 activity after oxidation of methionine residues.

Main Results:

• CTX3 exhibited greater inhibitory activity against Staphylococcus aureus (Gram-positive) than Escherichia coli (Gram-negative).
• CTX3's antibacterial activity positively correlated with increased bacterial membrane permeability and disruption of membrane integrity.
• CTX3 showed similar binding to LPS and LTA, with destabilization of LPS and inhibition of LTA biosynthesis enhancing its bactericidal effect.
• CTX3 notably permeabilized model membranes of S. aureus compared to E. coli.
• Oxidation of methionine residues in CTX3 reduced both membrane-permeabilizing and bactericidal activities.

Conclusions:

• CTX3's bactericidal activity is highly dependent on its ability to induce membrane permeability.
• Membrane damage is the primary mechanism underlying CTX3's antibacterial effects.
• CTX3's interaction with bacterial cell wall components influences its efficacy against different bacterial species.