Purification and cDNA cloning of salmorin that inhibits fibrinogen clotting

A new protein, salmorin, that inhibits fibrinogen clotting was purified to homogeneity from the snake venom of Agkistrodon halys brevicaudus. Salmorin was characterized to be a heterodimeric protein composed of 15 kDa and 14 kDa subunits. Purified salmorin inhibited not only thrombin-induced fibrinogen clotting but also factor Xa-induced prothrombin activation. Experimental evidence indicated that the hetero-dimeric protein does not bind to the thrombin catalytic site but binds to thrombin and prothrombin exosites. Analyses of the cDNA sequences encoding the two separate polypeptide chains revealed that the mature subunits are composed of 131 and 122 amino acids, respectively. In the isolated cDNAs, N-termini of both chains are preceded by hydrophobic signal peptides of 23 residues. The deduced amino acid sequence exhibited considerable identity with other snake venom C-type lectin-like proteins derived from various snake venoms.