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Phospholipase A2 myotoxins from Bothrops snake venoms
1Facultad de Microbiología, Universidad de Costa Rica, San José.
Summary
Bothrops snake venom contains myotoxins that cause muscle necrosis by interacting with cell membranes. These phospholipases A2 toxins can damage muscle tissue even without enzymatic activity.
Area of Science:
- Biochemistry
- Toxicology
- Molecular Biology
Background:
- Myotoxins from Bothrops snake venoms are primarily group II basic phospholipases A2.
- Some myotoxins, like Lys-49 variants, exhibit reduced or no enzymatic activity.
- These myotoxins form a family of structurally and antigenically related proteins found in various Bothrops and other crotalid venoms.
Purpose of the Study:
- To investigate the mechanism of action of Bothrops myotoxins in skeletal muscle necrosis.
- To explore the role of enzymatic activity and other molecular regions in myotoxin-induced damage.
- To propose a working hypothesis for the interaction of myotoxins with biological membranes.
Main Methods:
- Isolation and characterization of myotoxins from Bothrops snake venoms.
- In vivo studies involving intramuscular injection of myotoxins to observe muscle damage.
- In vitro studies assessing myotoxin-induced cytolysis and liposome disruption.
- Analysis of myotoxin structure-activity relationships, including the role of enzymatic activity.
Main Results:
- Bothrops myotoxins induce rapid skeletal muscle necrosis in vivo, initiated at the plasma membrane.
- Myotoxin-induced muscle damage and cell lysis can occur even when phospholipase A2 activity is inhibited.
- Evidence suggests a membrane-interacting region distinct from the catalytic site, involving basic and hydrophobic residues near the C-terminus.
- Calcium ion influx appears to be a key mediator in the muscle necrosis process.
Conclusions:
- Bothrops myotoxins possess potent myotoxic activity, leading to selective skeletal muscle necrosis.
- The mechanism of action involves interaction with biological membranes via a non-catalytic site, causing destabilization and ion permeability loss.
- While enzymatic activity may contribute, it is not essential for the primary myotoxic effects, suggesting alternative membrane-disrupting mechanisms.