α-Enolase of Streptococcus pneumoniae is a plasmin(ogen)-binding protein displayed on the bacterial cell surface
α-Enolase of Streptococcus pneumoniae is a plasmin(ogen)-binding protein displayed on the bacterial cell surface
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DOI：
10.1046/j.1365-2958.2001.02448.x
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发表时间：
2001-06-01
影响因子：
3.6
通讯作者：
Hammerschmidt, S
中科院分区：
文献类型：
--
作者：
Bergmann, S;Rohde, M;Hammerschmidt, S
人纤溶酶原与肺炎链球菌的结合及其随后的活化促进细菌穿透重建的基底膜。在这项研究中，我们的特点是一种新的肺炎球菌表面蛋白的分子量为47 kDa，指定Eno，它特异性结合人纤溶酶（原），表现出α-烯醇化酶活性，是必要的活力。使用酶分析，我们已经证实了α-烯醇化酶活性的肺炎球菌表面展示Eno和纯化的重组Eno蛋白。免疫电镜显示Eno存在于细胞质中，以及在表面上的封装和未封装的肺炎球菌。纤溶酶原结合活性证明与整个肺炎球菌细胞和纯化的Eno蛋白。还显示Eno与活化的纤溶酶原结合;然而，与纤溶酶原相比，对纤溶酶的亲和力显著降低。竞争性抑制试验的结果表明，通过纤溶酶（原）中的赖氨酸结合位点介导结合。羧肽酶B处理和Eno的C-末端赖氨酰残基的氨基酸取代表明，C-末端赖氨酸是纤溶酶（原）结合活性的关键。Eno广泛分布于肺炎球菌血清型中，结合实验表明分泌的Eno与细菌细胞表面重新结合。免疫电镜也证实了再结合。这些结果表明，纤溶酶原激活人类病原体的机制，可能有助于其在侵入性感染过程中的毒力潜力。
Binding of human plasminogen to Streptococcus pneumoniae and its subsequent activation promotes penetration of bacteria through reconstituted basement membranes. In this study, we have characterized a novel pneumococcal surface protein with a molecular mass of 47 kDa, designated Eno, which specifically binds human plasmin(ogen), exhibits alpha -enolase activity and is necessary for viability. Using enzyme assays, we have confirmed the alpha -enolase activity of both pneumococcal surface-displayed Eno and purified recombinant Eno protein. Immunoelectron microscopy indicated the presence of Eno in the cytoplasm as well as on the surface of encapsulated and unencapsulated pneumococci. Plasminogen-binding activity was demonstrated with whole pneumococcal cells and purified Eno protein. Binding of activated plasminogen was also shown for Eno; however, the affinity for plasmin is significantly reduced compared with plasminogen. Results from competitive inhibition assays indicate that binding is mediated through the lysine binding sites in plasmin(ogen). Carboxypeptidase B treatment and amino acid substitutions of the C-terminal lysyl residues of Eno indicated that the C-terminal lysine is pivotal for plasmin(ogen)-binding activity. Eno is ubiquitously distributed among pneumococcal serotypes, and binding experiments suggested the reassociation of secreted Eno to the bacterial cell surface. The reassociation was also confirmed by immunoelectron microscopy. The results suggest a mechanism of plasminogen activation for human pathogens that might contribute to their virulence potential in invasive infectious processes.