Thrombocytopenia occurs in a number of patients bitten by Bothrops asper, a species responsible for the majority of
snakebites in Central America and southern Mexico. In this work we describe the isolation of a new platelet-aggregating
protein, named
aspercetin, from the
venom of B. asper, which induces
thrombocytopenia in mice. Isolation was carried out by a combination of ion-exchange chromatography on
DEAE-
Sepharose and affinity chromatography on
Affi-Gel Blue.
Aspercetin is a
disulfide-linked heterodimer, with a pI of 4.5 and a molecular mass of 29,759 Da, detemined by MALDI-ESI mass spectrometry. N-terminal sequence shows homology with a number of
venom proteins which belong to the
C-type lectin family.
Aspercetin has functional similarities with
botrocetin, from B.
jararaca venom, since it induces platelet aggregation only in the presence of plasma or purified
von Willebrand factor.
Aspercetin-mediated platelet aggregation results from the interaction of
von Willebrand factor with platelet receptor GPIb.
Aspercetin lacks
anticoagulant effect and does not agglutinate erythrocytes, in contrast with other representatives of the
C-type lectin family isolated from
snake venoms. Moreover,
aspercetin is not lethal, nor does it induce myonecrosis,
hemorrhage and
edema. When injected intravenously or intramuscularly in mice it induces a rapid, dose-dependent drop in platelet counts and prolongs the bleeding time, suggesting that it may play a role in the
thrombocytopenia that develops in a number of B. asper envenomations. Moreover, mice injected intravenously with
aspercetin and then receiving an
intradermal injection of B. asper
hemorrhagic metalloproteinase BaP1 develop a larger hemorrhagic lesion than mice receiving only BaP1. This suggests that
aspercetin, by reducing platelet numbers, may