STRUCTURES OF THE NONCOVALENT COMPLEXES OF HUMAN AND BOVINE PROTHROMBIN FRAGMENT-2 WITH HUMAN PPACK-THROMBIN
STRUCTURES OF THE NONCOVALENT COMPLEXES OF HUMAN AND BOVINE PROTHROMBIN FRAGMENT-2 WITH HUMAN PPACK-THROMBIN
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DOI：
10.1021/bi00069a006
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发表时间：
1993-05-11
期刊：
影响因子：
2.9
通讯作者：
TULINSKY, A
中科院分区：
文献类型：
--
作者：
ARNI, RK;PADMANABHAN, K;TULINSKY, A
人和牛凝血酶原片段2（第二kringle）已分别与人PPACK（D-Phe-Pro-Arg）-凝血酶共结晶，这些非共价复合物的结构已被确定和细化（R = 0.155和0.157，分别）在3.3埃分辨率使用X-射线晶体学方法。Kringles与凝血酶在先前被认为是肝素结合区的位点相互作用。后者是靠近富含精氨酸和赖氨酸残基的凝血酶的C-末端螺旋的高度正电性表面。这些与Kringle 2的酸性侧链形成盐桥。有些出乎意料的是，kringle的负基团对应于赖氨酸结合kringle（如纤溶酶原K1和K4以及TPA K2）的赖氨酸结合位点的扩大的阴离子中心。凝血酶原kringle 2中的阴离子基序是DGDEE。赖氨酸结合位点区域的相应阳离子中心具有不利的Arg 70 Asp取代，但Lys 35是保守的。然而，片段2的折叠与凝血酶原kringle 1和其他kringle的折叠不同：第二个外环具有扭曲的两圈螺旋，第二个内环的发夹β-转角在Val 64和Asp 70处枢转60度。Lys 35位于螺旋的一个转角上，这导致它投射到片段2-凝血酶复合物中的溶剂空间中，从而破坏赖氨酸结合位点的阳离子中心的任何痕迹。由于没有报道片段2结合赖氨酸，它最有可能具有不同的第二外环的固有折叠构象，如也已观察到TPA K2和尿激酶kringle的情况。Val 64-Asp 70 β-转角的运动很可能是伴随络合的构象变化，这揭示了Kringles中迄今为止未被怀疑的新的柔性。片段2-凝血酶复合物仅是多结构域血液蛋白中待确定的第二个盒模块-催化结构域结构，并且仅是这些蛋白中待描述的第三个结构域-结构域相互作用，其他是没有Gla结构域的因子Xa和具有Gla结构域和kringle的Ca 2+凝血酶原片段1。
Both human and bovine prothrombin fragment 2 (the second kringle) have been cocrystallized separately with human PPACK (D-Phe-Pro-Arg)-thrombin, and the structures of these noncovalent complexes have been determined and refined (R = 0.155 and 0.157, respectively) at 3.3-angstrom resolution using X-ray crystallographic methods. The kringles interact with thrombin at a site that has previously been proposed to be the heparin binding region. The latter is a highly electropositive surface near the C-terminal helix of thrombin abundant in arginine and lysine residues. These form salt bridges with acidic side chains of kringle 2. Somewhat unexpectedly, the negative groups of the kringle correspond to an enlarged anionic center of the lysine binding site of lysine binding kringles such as plasminogens K1 and K4 and TPA K2. The anionic motif is DGDEE in prothrombin kringle 2. The corresponding cationic center of the lysine binding site region has an unfavorable Arg70Asp substitution, but Lys35 is conserved. However, the folding of fragment 2 is different from that of prothrombin kringle 1 and other kringles: the second outer loop possesses a distorted two-turn helix, and the hairpin beta-turn of the second inner loop pivots at Val64 and Asp70 by 60-degrees. Lys35 is located on a turn of the helix, which causes it to project into solvent space in the fragment 2-thrombin complex, thereby devastating any vestige of the cationic center of the lysine binding site. Since fragment 2 has not been reported to bind lysine, it most likely has a different inherent folding conformation for the second outer loop, as has also been observed to be the case with TPA K2 and the urokinase kringle. The movement of the Val64-Asp70 beta-turn is most likely a conformational change accompanying complexation, which reveals a new heretofore unsuspected flexibility in kringles. The fragment 2-thrombin complex is only the second cassette module-catalytic domain structure to be determined for a multidomain blood protein and only the third domain-domain interaction to be described among such proteins, the others being factor Xa without a Gla domain and Ca2+ prothrombin fragment 1 with a Gla domain and a kringle.