Bothrops asper myotoxin II (Mt-II)

Bothrops asper myotoxin II (Mt-II) is a non-enzymatic protein isolated from the venom of the terciopelo snake, Bothrops asper, and serves as a model member of the Lys49 phospholipase A2 (PLA2) homolog family. While it shares the structural scaffold of secreted PLA2 enzymes, the substitution of the catalytic aspartate at position 49 with a lysine residue renders it enzymatically inactive. Despite this lack of catalytic activity, Mt-II is a potent cytotoxin that induces severe skeletal muscle necrosis by directly disrupting the sarcolemma through its cationic and hydrophobic C-terminal region. This membrane perturbation leads to a massive influx of extracellular calcium ions and the release of intracellular stores, triggering rapid cell death and a robust inflammatory response. Clinically, it is a primary driver of the localized tissue damage, intense pain, and edema observed in snakebite victims, which can frequently lead to permanent disability if not addressed immediately. Because current antivenoms are often limited in their ability to neutralize the localized effects of such small, fast-acting toxins, Myotoxin II is considered a significant target for the development of alternative therapeutics like small-molecule inhibitors and synthetic peptides.

Other names

Lys49 phospholipase A2 homologMyotoxin IIPhospholipase A2-like proteinBasic phospholipase A2 homolog

Neutralizing agents and inhibitors function by binding to the cationic and hydrophobic regions of the toxin, particularly at its C-terminal effector site, thereby physically blocking its ability to interact with and destabilize the sarcolemma of muscle cells.