Mutations in Autolytic Loop-2 and at Asp554of Human Prothrombin That Enhance Protein C Activation by Meizothrombin*
Mutations in Autolytic Loop-2 and at Asp554of Human Prothrombin That Enhance Protein C Activation by Meizothrombin*
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人凝血酶原自溶 Loop-2 和 Asp554 的突变可增强 Mezothrombin 对蛋白 C 的激活*
DOI：
10.1074/jbc.m208220200
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
T. Morita
中科院分区：
文献类型：
--
作者：
H. Koike;D. Okuda;T. Morita
凝血酶在止血过程中作用于许多蛋白质底物。它对这些底物的特异性通过在远离凝血酶分子的活性位点（指定的外切位点）的区域的相互作用来调节。外位点相互作用可以是与底物、辅因子如血栓调节蛋白或来自凝血酶原的片段。α-凝血酶对纤维蛋白原的相对活性比对蛋白C的相对活性大10倍。然而，甲藻凝血酶对蛋白C的相对活性是对纤维蛋白原的14倍。凝血酶特异性的调节与其Na+结合位点和自溶环-2中与Na+结合位点相互作用的残基有关。产生重组甲藻凝血酶（rMT）和rMT脱片段1（rMT（desF 1））的重组凝血酶原能够比较Na+结合残基（Asp 554）突变和环-2缺失（Glu 466-Thr 469）对甲藻凝血酶对几种底物的相对活性的影响。α-凝血酶、重组α-凝血酶和rMT（desF 1）对叔丁氧羰基-VPR-对硝基苯胺的水解作用几乎相同，但rMT的水解作用仅为α-凝血酶的40%。已知rMT和rMT（desF 1）对纤维蛋白原的凝血作用是α-凝血酶的12-16%。然而，引人注目的是，尽管通过用Ala或Leu取代Asp 554或通过缺失环-2修饰的甲藻凝血酶分别具有α-凝血酶的6- 8%和<1%的凝血活性，但这些甲藻凝血酶对蛋白C的活性增加到α-凝血酶的10倍以上。有人提出，涉及自溶环-2和Na+结合位点的凝血酶内的相互作用主要增强凝血酶对纤维蛋白原的作用，但损害凝血酶对蛋白C的作用。
Thrombin acts on many protein substrates during the hemostatic process. Its specificity for these substrates is modulated through interactions at regions remote from the active site of the thrombin molecule, designated exosites. Exosite interactions can be with the substrate, cofactors such as thrombomodulin, or fragments from prothrombin. The relative activity of α-thrombin for fibrinogen is 10 times greater than that for protein C. However, the relative activity of meizothrombin for protein C is 14 times greater than that for fibrinogen. Modulation of thrombin specificity is linked to its Na+-binding site and residues in autolytic loop-2 that interact with the Na+-binding site. Recombinant prothrombins that yield recombinant meizothrombin (rMT) and rMT des-fragment 1 (rMT(desF1)) enable comparisons of the effects of mutations at the Na+-binding residue (Asp554) and deletion of loop-2 (Glu466–Thr469) on the relative activity of meizothrombin for several substrates. Hydrolysis of t-butoxycarbonyl-VPR-p-nitroanilide by α-thrombin, recombinant α-thrombin, or rMT(desF1) was almost identical, but that by rMT was only 40% of that by α-thrombin. Clotting of fibrinogen by rMT and rMT(desF1) was 12–16% of that by α-thrombin, as already known. Strikingly, however, although meizothrombins modified by substitution of Asp554 with either Ala or Leu or by deletion of loop-2 had 6–8 and <1%, respectively, of the clotting activity of α-thrombin, the activity of these meizothrombins for protein C was increased to >10 times that of α-thrombin. It is proposed that interactions within thrombin that involve autolytic loop-2 and the Na+-binding site primarily enhance thrombin action on fibrinogen, but impair thrombin action on protein C.
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影响因子：
2.9
作者：
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通讯作者：
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影响因子：
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作者：
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影响因子：
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作者：
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DOI：
--
发表时间：
1990
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Doyle,MF;Mann,KG
通讯作者：
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影响因子：
8.7
作者：
BOVILL, EG;TRACY, RP;MANN, KG
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