Calcium-binding analysis and molecular modeling reveal echis coagulation factor IX/factor X-binding protein has the Ca-binding properties and Ca ion-independent folding of other C-type lectin-like proteins.

Many biologically active heterodimeric proteins of snake venom consist of two C-type lectin-like subunits. One of these proteins, habu IX/X-bp, is a Gla domain-binding protein whose subunits both bind to a Ca2+ ion, with a total of two Ca2+-binding sites. The molecular modeling and Ca2+-binding analysis of echis IX/X-bp revealed that it lacks one of two Ca2+-binding sites, though the folding of this subunit is conserved. It is concluded that heterodimeric C-type lectin-like proteins function independent of Ca2+ and have essentially a similar folding to habu IX/X-bp.