Structure of myotoxin II, a catalytically inactive Lys49 phospholipase A2 homologue from Atropoides nummifer venom.

Lys49 snake-venom phospholipase A2 (PLA2) homologues are highly myotoxic proteins which, although lacking catalytic activity, possess the ability to disrupt biological membranes, inducing significant muscle-tissue loss and permanent disability in severely envenomed patients. Since the structural basis for their toxic activity is still only partially understood, the structure of myotoxin II, a monomeric Lys49 PLA2 homologue from Atropoides nummifer, has been determined at 2.08 angstroms resolution and the anion-binding site has been characterized.