Inhibition Of Crotoxin Binding To Rat Brain Synaptossomes By  A PLA2 Inhibitor From Crotalus durissus terrificus  Snake Plasma

^1,2Santos, R.M.M.; ²Oliveira, L. C; ²De Lima, M. E.; ²Santoro, M. M.; ¹Fortes-Dias, C. L.

1 Centro de Pesquisa e Desenvolvimento/FUNED, Belo Horizonte, Minas Gerais; 2 Departamento de Bioquímica e Imunologia/UFMG, Belo Horizonte, Minas Gerais.

The venom of Crotalusdurissus terrificus snakes is composed mainly of a b-neurotoxin, crotoxin (Ctx), which is know to contain the bulk of the lethal toxicity of the crude source. Ctx is a heterodimer composed of a basic, toxic PLA2 subunit (CB) and an acidic, non-toxic and enzymatically inactive subunit (CA). To prevent any damage to the snake, due to an accidental leaking of the venom, these reptiles possess an anti-toxic protein in their blood plasma. This protein, named CNF for Crotalus neutralizing factor, inhibits the PLA2 activity of crotoxin acting, therefore, as a soluble receptor for the toxin. The aim of the present study was to investigate the action of CNF upon the binding of Ctx to a biological membrane, under varying incubation conditions. Ctx was radiodinated and assayed against rat brain synaptosomes, in the presence of the unlabelled Ctx, the isolated subunits CA  or CB and CNF. CNF was able to inhibit the binding of Ctx and to displace the toxin already bound to its target, in a concentration dependent way.

Financial support: FAPEMIG and CNPq

Correspondence to: robertamarques3@zipmail.com.br