Mulichak A M, Tulinsky A
Department of Chemistry, Michigan State University, East Lansing 48824.
Blood Coagul Fibrinolysis. 1990 Dec;1(6):673-9.
Human plasminogen kringle 4, which crystallizes in the orthorhombic system a = 32.15(2), b = 49.01(2), c = 49.04(3) A, space group P2(1)2(1)2(1), four molecules per unit cell, protein volume fraction 0.62, has been determined at 1.9 A resolution. The structure was solved by rotation-translation methods using the structure of bovine prothrombin kringle 1 as a model and it has been refined at 1.9 A resolution to an R-value of 0.142. The root mean square (rms) deviation between the main-chain atoms of the two kringles is about 0.5 A while that between 31 conserved side chains is a surprisingly large 1.2 A. The structure of the lysine binding subsite of fibrin binding of kringle 4 is approximated well by prothrombin kringle 1 but with some notable exceptions. The latter transform the site from a non-binding kringle to one which recognizes lysine and other omega-amino-carboxylic acids. The binding site of the observed kringle 4 structure is also compared with one that was modelled from the structure of kringle 1 of prothrombin fragment 1 and NMR observations. Arginine residues of the binding site of a neighbouring molecule make ion pairs with aspartic acid residues in the binding site of another molecule in the kringle 4 structure.
人纤溶酶原kringle 4晶体属于正交晶系，a = 32.15(2)，b = 49.01(2)，c = 49.04(3) Å，空间群为P2(1)2(1)2(1)，每个晶胞含四个分子，蛋白质体积分数为0.62，其结构已在1.9 Å分辨率下测定。该结构以牛凝血酶原kringle 1的结构为模型，通过旋转平移法解析得到，并在1.9 Å分辨率下精修至R值为0.142。两个kringle主链原子之间的均方根（rms）偏差约为0.5 Å，而31个保守侧链之间的偏差则高达1.2 Å，令人惊讶。kringle 4与纤维蛋白结合的赖氨酸结合亚位点的结构与凝血酶原kringle 1的结构大致相似，但也有一些显著差异。后者将该位点从一个非结合kringle转变为一个能识别赖氨酸和其他ω-氨基羧酸的位点。还将观察到的kringle 4结构的结合位点与根据凝血酶原片段1的kringle 1结构和核磁共振观察结果模拟得到的结合位点进行了比较。在kringle 4结构中，相邻分子结合位点的精氨酸残基与另一个分子结合位点的天冬氨酸残基形成离子对。
