Kannan T R, Provenzano D, Wright J R, Baseman J B
Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, USA.
Infect Immun. 2005 May;73(5):2828-34. doi: 10.1128/IAI.73.5.2828-2834.2005.
Mycoplasma pneumoniae infections represent a major primary cause of human respiratory diseases, exacerbate other respiratory disorders, and are associated with extrapulmonary pathologies. Cytadherence is a critical step in mycoplasma colonization, aided by a network of mycoplasma adhesins and cytadherence accessory proteins which mediate binding to host cell receptors. Furthermore, the respiratory mucosa is enriched with extracellular matrix components, including surfactant proteins, fibronectin, and mucin, which provide additional in vivo targets for mycoplasma parasitism. In this study we describe interactions between M. pneumoniae and human surfactant protein-A (hSP-A). Initially, we found that viable M. pneumoniae cells bound to immobilized hSP-A in a dose- and calcium (Ca(2+))-dependent manner. Mild trypsin treatment of intact mycoplasmas reduced binding markedly (80 to 90%) implicating a surface-associated mycoplasma protein(s). Using hSP-A-coupled Sepharose affinity chromatography and polyacrylamide gel electrophoresis, we identified a 65-kDa hSP-A binding protein of M. pneumoniae. The presence of Ca(2+) enhanced binding of the 65-kDa protein to hSP-A, which was reduced by the divalent cation-chelating agent, EDTA. The 65-kDa hSP-A binding protein of M. pneumoniae was identified by sequence analysis as a novel protein (MPN372) possessing a putative S1-like subunit of pertussis toxin at the amino terminus (amino acids 1 to 226), with the remaining amino acids (227 to 591) exhibiting no homology with other subunits of pertussis toxin, other known toxins, or any reported proteins. Recombinant MPN372 (MPN372) bound to hSP-A in a dose-dependent manner, which was markedly reduced by preincubation with mouse recombinant MPN372 antisera. Also, adherence of viable M. pneumoniae cells to hSP-A was inhibited by recombinant MPN372 antisera, demonstrating that MPN372, a previously designated hypothetical protein, is surface exposed and mediates mycoplasma attachment to hSP-A.
肺炎支原体感染是人类呼吸道疾病的主要原发性病因，会加重其他呼吸道疾病，并与肺外病变有关。细胞黏附是支原体定植的关键步骤，由支原体黏附素和细胞黏附辅助蛋白网络辅助，这些蛋白介导与宿主细胞受体的结合。此外，呼吸道黏膜富含细胞外基质成分，包括表面活性蛋白、纤连蛋白和黏蛋白，这些为支原体寄生提供了额外的体内靶点。在本研究中，我们描述了肺炎支原体与人表面活性蛋白-A（hSP-A）之间的相互作用。最初，我们发现活的肺炎支原体细胞以剂量和钙（Ca(2+)）依赖的方式与固定化的hSP-A结合。用温和的胰蛋白酶处理完整的支原体可显著降低结合（80%至90%），这表明存在一种与表面相关的支原体蛋白。使用hSP-A偶联的琼脂糖亲和层析和聚丙烯酰胺凝胶电泳，我们鉴定出肺炎支原体的一种65 kDa的hSP-A结合蛋白。Ca(2+)的存在增强了65 kDa蛋白与hSP-A的结合，而二价阳离子螯合剂乙二胺四乙酸（EDTA）则降低了这种结合。通过序列分析，肺炎支原体的65 kDa hSP-A结合蛋白被鉴定为一种新蛋白（MPN372），其氨基末端（氨基酸1至226）具有假定的百日咳毒素S1样亚基，其余氨基酸（227至591）与百日咳毒素的其他亚基、其他已知毒素或任何已报道的蛋白均无同源性。重组MPN372（MPN372）以剂量依赖的方式与hSP-A结合，与小鼠重组MPN372抗血清预孵育后，这种结合显著降低。此外，重组MPN372抗血清抑制了活的肺炎支原体细胞与hSP-A的黏附，表明MPN372（一种先前被指定的假定蛋白）暴露于表面，并介导支原体与hSP-A的附着。
