Friedrich Rainer, Panizzi Peter, Fuentes-Prior Pablo, Richter Klaus, Verhamme Ingrid, Anderson Patricia J, Kawabata Shun-Ichiro, Huber Robert, Bode Wolfram, Bock Paul E
Abteilung Strukturforschung, Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany.
Nature. 2003 Oct 2;425(6957):535-9. doi: 10.1038/nature01962.
Many bacterial pathogens secrete proteins that activate host trypsinogen-like enzyme precursors, most notably the proenzymes of the blood coagulation and fibrinolysis systems. Staphylococcus aureus, an important human pathogen implicated in sepsis and endocarditis, secretes the cofactor staphylocoagulase, which activates prothrombin, without the usual proteolytic cleavages, to directly initiate blood clotting. Here we present the 2.2 A crystal structures of human alpha-thrombin and prethrombin-2 bound to a fully active staphylocoagulase variant. The cofactor consists of two domains, each with three-helix bundles; this is a novel fold that is distinct from known serine proteinase activators, particularly the streptococcal plasminogen activator streptokinase. The staphylocoagulase fold is conserved in other bacterial plasma-protein-binding factors and extracellular-matrix-binding factors. Kinetic studies confirm the importance of isoleucine 1 and valine 2 at the amino terminus of staphylocoagulase for zymogen activation. In addition to making contacts with the 148 loop and (pro)exosite I of prethrombin-2, staphylocoagulase inserts its N-terminal peptide into the activation pocket of bound prethrombin-2, allosterically inducing functional catalytic machinery. These investigations demonstrate unambiguously the validity of the zymogen-activation mechanism known as 'molecular sexuality'.
许多细菌病原体分泌能激活宿主类胰蛋白酶原酶前体的蛋白质，最显著的是凝血和纤维蛋白溶解系统的酶原。金黄色葡萄球菌是一种与败血症和心内膜炎有关的重要人类病原体，它分泌辅因子葡萄球菌凝固酶，该酶可激活凝血酶原，无需通常的蛋白水解切割，就能直接启动血液凝固。在此，我们展示了与完全活性的葡萄球菌凝固酶变体结合的人α-凝血酶和凝血酶原-2的2.2埃晶体结构。该辅因子由两个结构域组成，每个结构域都有三个螺旋束；这是一种与已知丝氨酸蛋白酶激活剂不同的新型折叠结构，特别是与链球菌纤溶酶原激活剂链激酶不同。葡萄球菌凝固酶的折叠结构在其他细菌血浆蛋白结合因子和细胞外基质结合因子中是保守的。动力学研究证实了葡萄球菌凝固酶氨基末端的异亮氨酸1和缬氨酸2对酶原激活的重要性。除了与凝血酶原-2的148环和（前）外位点I接触外，葡萄球菌凝固酶还将其N端肽插入结合的凝血酶原-2的激活口袋中，通过变构诱导功能性催化机制。这些研究明确证明了被称为“分子性别”的酶原激活机制的有效性。
