Received: December 20, 2004, Accepted: May 18, 2005, Published online: October 30, 2005.

CROTACETIN, A NOVEL SNAKE VENOM C-TYPE LECTIN, IS HOMOLOG OF CONVULXIN

RÁDIS-BAPTISTA G. (1), MORENO F. B. M. B. (1), NOGUEIRA L. L. (1), MARTINS A. M. C. (2), TOYAMA D. O. (3), TOYAMA M. H. (4), AZEVEDO JR W. F. (5), CAVADA B. S. (1), YAMANE T. (6)

(1) Department of Biochemistry and Molecular Biology, Federal University of Ceará (UFC), Ceará, Brazil; (2) Department of Clinical and Toxicological Analyses, Federal University of Ceará (UFC), Ceará, Brazil; (3) Department of Biochemistry, State University of Campinas (UNICAMP), São Paulo, Brazil; (4) Department of Chemistry, São Paulo State University (UNESP), São Paulo, Brazil; (5) Department of Physics, Institute of Biosciences, Humanities and Exact Sciences, São Paulo State University (UNESP), São Paulo, Brazil; (6) Molecular Biology Center, Institute of Nuclear Energy and Research (IPEN), São Paulo, Brazil.

ABSTRACT: 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.

KEY WORDS: Crotalus durisssus venom, snake venom C-type lectin, homology modeling, platelet aggregation, antimicrobial activity.

CORRESPONDENCE TO:

GANDHI RÁDIS-BAPTISTA, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Campus do Picí, Caixa Postal 6020, 60451-970, Fortaleza, Ceará, Brazil. Phone: +55 85 4008 9817. Fax: +55 85 4008 9789. Email: radisbra@ufc.br