ABSTRACT
Bothropstoxin-II a calcium-dependent enzyme from Bothrops jararacussu venom causes tissue damage and several haemostatic disorders including platelet aggregation. In order to elucidate the structural determinants of its multiple pharmacological activities, we have studied the effects of suramin on Bothropstoxin-II and present details concerning the mode of binding.
Subject(s)
Crotalid Venoms/chemistry , Crotalid Venoms/pharmacology , Group II Phospholipases A2/chemistry , Group II Phospholipases A2/pharmacology , Reptilian Proteins/chemistry , Reptilian Proteins/pharmacology , Algorithms , Animals , Binding Sites , Bothrops , Catalytic Domain , Computer Simulation , Creatine Kinase/metabolism , Crotalid Venoms/metabolism , Electrophoresis, Polyacrylamide Gel , Group II Phospholipases A2/metabolism , Mice , Models, Molecular , Protein Conformation , Reptilian Proteins/metabolism , Scattering, Small Angle , Suramin/metabolismABSTRACT
Lys49 phospholipase A2 homologues are highly myotoxic and cause extensive tissue damage but do not display hydrolytic activity towards natural phospholipids. The binding of heparin, heparin derivatives and polyanionic compounds such as suramin result in partial inhibition (up to 60%) of the myotoxic effects due to a change in the overall charge of the interfacial surface. In vivo experiments demonstrate that polyethylene glycol inhibits more than 90% of the myotoxic effects without exhibiting secondary toxic effects. The crystal structure of bothropstoxin-I complexed with polyethylene glycol reveals that this inhibition is due to steric hindrance of the access to the PLA2-active site-like region. These two inhibitory pathways indicate the roles of the overall surface charge and free accessibility to the PLA2-active site-like region in the functioning of Lys49 phospholipases A2 homologues. Molecular dynamics simulations, small angle X-ray scattering and structural analysis indicate that the oligomeric states both in solution and in the crystalline states of Lys49 phospholipases A2 are principally mediated by hydrophobic contacts formed between the interfacial surfaces. These results provide the framework for the potential application of both clinically approved drugs for the treatment of Viperidae snakebites.
