When linked to subunit A of IX/X-bp, anticoagulant protein which binds to the gamma-carboxyglutamic acid-domain regions of factors IX (F9) and factor X (10) in the presence of calcium with a 1 to 1 stoichiometry. When linked to subunit A of IX-bp, anticoagulant protein which binds to the gamma-carboxyglutamic acid-domain regions of factor IX (but not to factor X) in the presence of calcium with a 1 to 1 stoichiometry. Heterodimer with subunit A of IX/X-bp or IX-bp; disulfide-linked. Expressed by the venom gland. Calcium is required for ligand binding. Belongs to the snaclec family.