Probing the interface between factor Xa and tissue factor in the quaternary complex tissue factor-factor VIIa-factor Xa-tissue factor pathway inhibitor
Probing the interface between factor Xa and tissue factor in the quaternary complex tissue factor-factor VIIa-factor Xa-tissue factor pathway inhibitor
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DOI：
10.1046/j.1432-1033.2003.03625.x
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发表时间：
2003-06-01
期刊：
影响因子：
--
通讯作者：
Svensson, M
中科院分区：
文献类型：
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作者：
Carlsson, K;Freskgård, PO;Svensson, M
凝血是由VIIa因子（FVIIa）及其辅助因子组织因子（TF）之间形成的复合物引发的。组织因子通路抑制剂（TFPI）对TF-FVIIa的抑制分两步进行：首先TFPI结合到Xa因子的活性位点（FXa），然后FXa-TFPI对TF-FVIIa进行反馈抑制。TFPI对TF-FVIIa活性的依赖抑制导致了四元复合物TF-FVIIa- fxa -TFPI的形成。我们使用定点荧光探测来绘制可溶性TF （sTF）在sTF- fvia -FXa- tfpi中与FXa相互作用的部分区域。我们发现sTF的c端区域，包括163、166、200和201位，参与了复合物中FXa的结合，FXa很可能通过其Gla结构域，也在这部分结合区与FVIIa的Gla结构域接触。此外，包括TF2结构域n端部分和TF1结构域c端部分的区域，即残基104和197，参与了四元配合物中FXa的相互作用。此外，对四元配合物sTF- fvii - fxa - tfpi与三元配合物sTF- fvii - fxa或sTF- fviia -FX中sTF和FX的相互作用区域(a)的比较显示出很大的相似性。
Blood coagulation is triggered by the formation of a complex between factor VIIa (FVIIa) and its cofactor, tissue factor (TF). TF-FVIIa is inhibited by tissue factor pathway inhibitor (TFPI) in two steps: first TFPI is bound to the active site of factor Xa (FXa), and subsequently FXa-TFPI exerts feedback inhibition of TF-FVIIa. The FXa-dependent inhibition of TF-FVIIa activity by TFPI leads to formation of the quaternary complex TF-FVIIa-FXa-TFPI. We used site-directed fluorescence probing to map part of the region of soluble TF (sTF) that interacts with FXa in sTF-FVIIa-FXa-TFPI. We found that the C-terminal region of sTF, including positions 163, 166, 200 and 201, is involved in binding to FXa in the complex, and FXa, most likely via its Gla domain, is also in contact with the Gla domain of FVIIa in this part of the binding region. Furthermore, a region that includes the N-terminal part of the TF2 domain and the C-terminal part of the TF1 domain, i.e. the residues 104 and 197, participates in the interaction with FXa in the quaternary complex. Moreover, comparisons of the interaction areas between sTF and FX(a) in the quaternary complex sTF-FVIIa-FXa-TFPI and in the ternary complexes sTF-FVII-FXa or sTF-FVIIa-FX demonstrated large similarities.