Huntington J A, Olson S T, Fan B, Gettins P G
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Biochemistry. 1996 Jul 2;35(26):8495-503. doi: 10.1021/bi9604643.
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.
需要肝素诱导的构象变化才能将抗凝血酶从因子Xa的缓慢抑制剂转变为快速抑制剂。有人提出[范·博克尔等人（1994年），《自然结构生物学》1，423 - 425]，反应中心残基P14在天然抗凝血酶中插入β-折叠A，通过肝素结合从β-折叠中移位，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。为了验证这一假设，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该变体对因子Xa的部分激活，我们得出结论，就环排出而言，所提出的肝素激活机制是正确的，因此有可能通过合适的铰链区替代来创建更高度激活的抗凝血酶变体。
