Glycoprotein Ib-binding protein from the venom of Deinagkistrodon acutus -cDNA sequence, functional characterization, and three-dimensional modeling

Agkicetin-C, a potent glycoprotein Ib antagonist from the venom of the Chin ese pit viper, Deinagkistrodon acutus, has been purified and characterized (5). It is a disulfide-linked heterodimer containing subunits of 132 and of 123 amino acid residues. Herein, the complete amino acid sequences were re solved by cloning and nucleotide sequencing of the cDNAs. The sequences of its subunits are homologous to those of other snake venom proteins of the C -type (Ca2+-dependent) lectin superfdmily. A three-dimensional model of agk icetin-C was constructed based on the crystal structure of habu coagulation factor IX/X-binding protein. By careful alignment of all the related seque nces available and comparing the 3D-model of agkicetin-C with structures of other homologous proteins of different functions, some variable residues o f agkicetin-C were identified, which possibly are responsible for the speci ficity of this distinct subtype of the C-type lectin-like venom proteins.