Ca(2+) -induced binding of anticoagulation factor II from the venom of Agkistrodon acutus with factor IX.
Anticoagulation factor II (ACF II), a coagulation factor X- binding protein from the venom of Agkistrodon acutus has both anticoagulant and hypotensive activities. Previous studies show that ACF II binds specifically with activated factor X (FXa) in a Ca(2+) -dependent manner and inhibits intrinsic coagulation pathway. In this study, the inhibition of extrinsic coagulation pathway by ACF II was measured in vivo by prothrombin time assay and the binding of ACF II to factor IX (FIX) was investigated by native polyacrylamide gel electrophoresis and surface plasmon resonance (SPR). The results indicate that ACF II also inhibits extrinsic coagulation pathway, but does not inhibit thrombin activity. ACF II also binds with FIX with high binding affinity in a Ca(2+) -dependent manner and their maximal binding occurs at about 0.1 mM Ca(2+) . ACF II has similar binding affinity to FIX and FX as determined by SPR. Ca(2+) has a slight effect on the secondary structure of FIX as determined by circular dichroism spectroscopy. Ca(2+) ions are required to maintain in vivo function of FIX Gla domain for its recognition of ACF II. However, Ca(2+) at high concentrations (>0.1 mM) inhibits the binding of ACF II to FIX. Ca(2+) functions as a switch for the binding between ACF II and FIX. ACF II extends activated partial thromboplastin time more strongly than prothrombin time, suggesting that the binding of ACF II with FIX may play a dominant role in the anticoagulation of ACF II in vivo.
Department of Chemistry, University of Science and Technology of China, Hefei, 230026, People's Republic of China.
Deng-Ke
DK
Shen
Xiao-Long
XL
Xu
Yan
Y
Zhang
Jia-Jia
JJ
Song
Xin-Cheng
XC
Yan
Ming-Chun
MC
Guo
D017836:Agkistrodon; D000818:Animals; D001777:Blood Coagulation / Q000187:drug effects; D002118:Calcium / Q000737:chemistry*; D002942:Circular Dichroism; D003435:Crotalid Venoms / Q000737:chemistry* / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005164:Factor IX / Q000737:chemistry*; D051381:Rats; D020349:Surface Plasmon Resonance
D003435:Crotalid Venoms; C465285:anticoagulation factor I, Agkistrodon acutus; D005164:Factor IX; D002118:Calcium