Crotacetin, a novel snake venom C-type lectin, is homolog of convulxin

Snake venom (sv) C-type lectins encompass a group of hemorrhagic toxins, which are able to interfere with hemostasis. They share significant similarity in their primary structures with C-type lectins of other animals, and also present a conserved carbohydrate recognition domain (CRD). A very well studied sv C-type lectin is the heterodimeric toxin, convulxin (CVX), from the venoms of South American rattlesnakes, Crotalus durissus terrificus and C. d. cascavella. It consists of two subunits, alfa (CVXa, 13.9 kDa) and beta (CVXb, 12.6 kDa), joined by inter and intra-chain disulfide bounds, and is arranged in a tetrameric a4b4 conformation. Convulxin is able to activate platelet and induce their aggregation by acting via p62/GPVI collagen receptor. Several cDNA precursors, homolog of CVX subunits, were cloned by PCR homology screening. As determined by computational analysis, one of them, named crotacetin b subunit, was predicted as a polypeptide with a tridimensional conformation very similar to other subunits of convulxin-like snake toxins. Crotacetin was purified from C. durissus venoms by gel permeation and reverse phase high performance liquid chromatography. The heterodimeric crotacetin is expressed in the venoms of several C. durissus subspecies, but it is prevalent in the venom of C. durissus cascavella. As inferred from homology modeling, crotacetin induces platelet aggregation but noticeably exhibits antimicrobial activity against Gram-positive and Gram-negative bacteria

Modelo de intercambio de material lipídico entre liposomas de lecitina y trombocitos humanos intactos / Model of interchange of lipid material between lecithin liposomes and intact human thrombocytes

Plaquetas intactas, aisladas por centrifugación y lavado (a partir del plasma sanguíneo humano, obtenido de sangre citratada) fueron incubadas durante 3 horas en medio salino con liposomas de lecitina de yema de huevo marcados radiactivamente y obtenidos por el método de dilución en detergente. La mezcla fue separada por centrifugación. Se encontró una incorporación de fosfolipidos liposomales a las plaquetas por debajo del 1% del existente en la mezcla de incubación, según cuantificación de fosfolipidos y de marcaje radiactivo. El 68,6% del marcaje incorporado se encontró en la fosfatidilcolina (PC) y el 13,5% del mismo en la fosfatidiletanolamina (PE), después de cromatografía en capa delgada (TLC) del extracto lipídico del sedimento de plaquetas previamente incubadas