REFINED STRUCTURE OF THE HIRUDIN-THROMBIN COMPLEX
REFINED STRUCTURE OF THE HIRUDIN-THROMBIN COMPLEX
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DOI：
10.1016/0022-2836(91)80074-5
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发表时间：
1991-09-20
影响因子：
5.6
通讯作者：
HUBER, R
中科院分区：
文献类型：
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作者：
RYDEL, TJ;TULINSKY, A;HUBER, R
重组水蛭素（变体 2，Lys47）人 α-凝血酶复合物的结构已使用限制最小二乘法精修至晶体学 R 因子为 0·173。水蛭素结构由折叠成球状单元的 N 端结构域和呈延长链构象的长 17 肽 C 端组成。 N 末端结构域结合在凝血酶的活性位点，其中 Ilel' 至 Tyr3' 渗透到催化三联体。水蛭素Ilel'的α-氨基与凝血酶Ser195的OG形成氢键，Ilel'和Tyr3'的侧链占据非极性位点。 Thr2' 位于 S1 特异性位点的入口处，但不进入 S1 特异性位点，Ilel' 至 Tyr3' 与 Ser214 至 Gly219 形成平行的 β 链。后一种相互作用在所有其他丝氨酸蛋白酶-蛋白质抑制剂复合物中是反平行的。水蛭素的延伸 C 末端片段富含酸性残基，与纤维蛋白原结合外位点产生许多静电相互作用，而最后 5 个残基处于 310 度螺旋圈中，位于凝血酶表面的疏水斑块中。这两个分子所表现出的互补性的精确性产生了许多相互作用，虽然独立时通常较弱，但共同导致了高度的亲和力和特异性。尽管水蛭素-凝血酶和d-Phe-Pro-Arg-氯甲基酮-凝血酶在自溶环中的构象不同（Lys145至Gly150），但这很可能是由于不同的晶体堆积相互作用造成的，并且两者之间圆二色性的变化可能是由于环固有的灵活性。 RGD 序列通常已知参与细胞表面受体相互作用，出现在凝血酶中，并与充满水分子的长溶剂通道相关，该溶剂通道从 S1 位点末端通向表面。然而，RGD 三联体似乎无法在表面结合模式下协同相互作用。
The structure of a recombinant hirudin (variant 2, Lys47) human α-thrombin complex has been refined using restrained least-squares methods to a crystallographicR-factor of 0·173. The hirudin structure consists of an N-terminal domain folded into a globular unit and a long 17-peptide C-terminal in an extended chain conformation. The N-terminal domain binds at the active-site of thrombin where Ilel' to Tyr3' penetrates to the catalytic triad. The α-amino group of Ilel' of hirudin makes a hydrogen bond with OG of Ser195 of thrombin, the side-chains of Ilel' and Tyr3' occupy the apolar site. Thr2' is at the entrance to, but does not enter, the S1 specificity site and Ilel' to Tyr3' form a parallel β-strand with Ser214 to Gly219. The latter interaction is antiparallel in all other serine proteinase-protein inhibitor complexes. The extended C-terminal segment of hirudin, which is abundant in acidic residues, makes many electrostatic interactions with the fibrinogen binding exosite while the last five residues are in a 310helical turn residing in a hydrophobic patch on the thrombin surface. The precision of the complementarity displayed by these two molecules produces numerous interactions, which although independently generally weak, together are responsible for the high degree of affinity and specificity. Although hirudin-thrombin andd-Phe-Pro-Arg-chloromethyl ketone-thrombin differ in conformation in the autolysis loop (Lys145 to Gly150), this is most likely due to different crystal packing interactions and changes in circular dichroism between the two are probably due to the inherent flexibility of the loop. An RGD sequence, which is generally known to be involved in cell surface receptor interactions, occurs in thrombin and is associated with a long solvent channel filled with water molecules leading to the surface from the end of the S1 site. However, the RGD triplet does not appear to be able to interact in concert in a surface binding mode.