Mechanism of heparin activation of antithrombin. Evidence for reactive center loop preinsertion with expulsion upon heparin binding
Mechanism of heparin activation of antithrombin. Evidence for reactive center loop preinsertion with expulsion upon heparin binding
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DOI：
10.1021/bi9604643
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发表时间：
1996-07-02
期刊：
影响因子：
2.9
通讯作者：
Gettins, PGW
中科院分区：
文献类型：
--
作者：
Huntington, JA;Olson, ST;Gettins, PGW
需要肝素诱导的构象变化才能将抗凝血酶从缓慢的 Xa 因子抑制剂转变为快速的 Xa 因子抑制剂。已经有人提出[van Boeckel 等人。 (1994) 国家。结构。生物。 [1, 423-425] 反应中心残基 P14 插入天然抗凝血酶中的 β-折叠片 A 中，并通过肝素结合从 β-折叠片上移位，从而改变反应中心的构象，使其成为因子 Xa 结合的更好靶点。为了检验这一假设，我们对 P14 丝氨酸 --> 色氨酸抗凝血酶变体进行了表征。从肝素结合时色氨酸荧光的变化、对肝素亲和力的增加以及针对因子Xa的变体的部分激活，我们得出结论，所提出的肝素激活机制在环排出方面是正确的，因此可能通过合适的铰链区取代产生更高活化的抗凝血酶变体。
A heparin-induced conformational change is required to convert antithrombin from a slow to a fast inhibitor of factor Xa. It has been proposed [van Boeckel et al. (1994) Nat. Struct. Biol. 1, 423-425] that the reactive center residue P14 is inserted into beta-sheet A in native antithrombin and is displaced from the beta-sheet by heparin binding, thereby altering the conformation of the reactive center and making it a better target for factor Xa binding. To test this hypothesis, we have characterized a P14 serine --> tryptophan antithrombin variant. From changes in tryptophan fluorescence upon heparin binding, increased affinity for heparin, and partial activation of the variant against factor Xa, we conclude that the proposed mechanism of heparin activation is correct with respect to loop expulsion and that it may consequently be possible to create more highly activated antithrombin variants through suitable hinge region substitutions.