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Structural study of the interaction of crotoxin and their subunits with model membranes

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Carlos Roberto Natal Junior
Total Authors: 1
Document type: Master's Dissertation
Press: Botucatu. 2020-03-03.
Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu
Defense date:
Advisor: Marcos Roberto de Mattos Fontes; Roberto Morato Fernandez

Crotoxin (CTX) is the most abundant toxin present in Crotalus durissus terrificus venom, representing about 60% of its dry weight. CTX has neurotoxic, myotoxic and coagulant activities, being the main responsible for the high death rate in snakebite accidents caused by Crotalus snakes. Additionally, crotoxin actions with possible therapeutic applications were recently discovered, due to its anti-inflammatory, analgesic, immunomodulatory and antitumor effects. CTX is a heterodimer composed of two subunits, one acidic (CA) and the other basic (CB). CB is a phospholipase A2 with presynaptic activity blocking neuromuscular transmission that causes motor and respiratory paralysis in animals. Although the crystallographic and small angle X-ray scattering (SAXS) structures of CTX and CB have been resolved, their mechanism of action on cell membranes and the exact protein interaction sites with membranes are poorly understood. Lipids DMPC and DMPG were used to study the interaction on between these proteins and model membranes. Molecular biophysics techniques, such as static and time-resolved fluorescence spectroscopy and small angle X-ray scattering, were used to study the behavior of these proteins in presence of liposomes. The data obtained indricothere absence of interaction between CA and CTX with zwitterionic lipids (DMPC), while pointed the interaction between CB with both lipid systems (DMPC and DMPG). In the negatively charged model membrane samples (DMPG), it was possible to identify the interaction of CA and CTX with these membranes, which did not interact with the DMPC vesicles. CA did not cause bilayer lysis, while CTX triggered lipid lysis. Finally, the results suggested that CA dissociates from CB when CTX heterodimer approaches the liposomes. (AU)

FAPESP's process: 18/05090-1 - Structural study of the interaction of crotoxin and their subunits with model membranes and inhibitors
Grantee:Carlos Roberto Natal Junior
Support Opportunities: Scholarships in Brazil - Master