Ting L M, Hsia R C, Haidaris C G, Bavoil P M
Department of Microbiology and Immunology, University of Rochester Medical Center, New York 14642, USA.
Infect Immun. 1995 Sep;63(9):3600-8. doi: 10.1128/iai.63.9.3600-3608.1995.
The chlamydial life cycle involves the intimate interaction of components of the infectious elementary body (EB) surface with receptors on the susceptible eukaryotic cell plasma membrane. We have developed an in vitro ligand binding assay system for the identification and characterization of detergent-extracted EB envelope proteins capable of binding to glutaraldehyde-fixed HeLa cell surfaces. With this assay, the developmentally regulated cysteine-rich envelope protein Omp2 of Chlamydia psittaci strain guinea pig inclusion conjunctivitis was shown to bind specifically to HeLa cells. HeLa cells bound Omp2 selectively over other cell wall-associated proteins, including the major outer membrane protein, and the binding of Omp2 was abolished under conditions which alter its conformation. Furthermore, trypsin treatment, which reduces EB adherence, resulted in the proteolytic removal of a small terminal peptide of Omp2 at the EB surface and inactivated Omp2 in the ligand binding assay, while having a negligible effect on the major outer membrane protein. Collectively, our results suggest that Omp2 possesses the capacity to engage in a specific interaction with the host eukaryotic cell. We speculate that, since Omp2 is present only in the infectious EB form, the observed in vitro interaction may be representative of a determining step of the chlamydial pathogenic process.
衣原体的生命周期涉及感染性原体（EB）表面成分与易感真核细胞质膜上受体的密切相互作用。我们开发了一种体外配体结合测定系统，用于鉴定和表征能够结合戊二醛固定的HeLa细胞表面的去污剂提取的EB包膜蛋白。通过该测定，鹦鹉热衣原体豚鼠包涵体结膜炎菌株发育调控的富含半胱氨酸的包膜蛋白Omp2被证明能特异性结合HeLa细胞。与包括主要外膜蛋白在内的其他细胞壁相关蛋白相比，HeLa细胞选择性地结合Omp2，并且在改变其构象的条件下，Omp2的结合被消除。此外，胰蛋白酶处理可降低EB的粘附性，导致EB表面Omp2的一个小末端肽被蛋白水解去除，并在配体结合测定中使Omp2失活，而对主要外膜蛋白的影响可忽略不计。总体而言，我们的结果表明Omp2具有与宿主真核细胞进行特异性相互作用的能力。我们推测，由于Omp2仅存在于感染性EB形式中，观察到的体外相互作用可能代表衣原体致病过程的一个决定性步骤。
