Anticoagulant protein which binds to coagulation factor IX (F9) and coagulation factor X (F10) in the presence of calcium. It may bind the gamma-carboxyglutamic acid-domain regions of factors with a 1 to 1 stoichiometry. The dissociation constant (K(d)) are 6.6 nM for factor IX (F9) and 125 nM for factor X (F10). Does not bind carbohydrates. Heterodimer of subunits A and B; disulfide-linked. Expressed by the venom gland. Belongs to the snaclec family.