Mycoplasma pneumoniae is a frequent cause of community-acquired infections of the human respiratory tract. During the evolutionary adaptation of the bacteria to the host, the genome of the pathogen is strongly reduced resulting in the loss of cell wall, limited metabolic pathways and a relatively small number of virulence factors. As interacting with host proteins, surface-exposed proteins with a primary function in cytosol-located processes of metabolism and regulation such as glycolytic enzymes, heat-shock proteins and chaperones have been considered as contributing to pathogenesis. Among these moonlighting proteins, some members are confirmed as binding to several host components. The glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of M. pneumoniae is a typical example of such multi-binding proteins. To investigate the organization of these interactions, GAPDH was divided into four parts. Recombinant proteins were successfully expressed in Escherichia coli and polyclonal antisera were produced. Binding of full length and parts of GAPDH to human A549 cells was proven. Furthermore, interactions with human plasminogen, vitronectin, fibronectin and fibrinogen were demonstrated for nearly all recombinant GAPDH proteins. In the presence of these proteins, plasminogen can be activated to the protease plasmin. In contrast, the localization on the surface of bacterial cell was confirmed for the C-terminal part of GAPDH only. By using overlapping peptides covering this region, binding of the investigated host components to the sequence ³²⁶QLVRVVNYCAKL³³⁷ was found. The results of the study suggest a prominent role of the surface-localized C-terminal part of GAPDH in associations with different human proteins indicating its importance for host-pathogen-interactions.

肺炎支原体是社区获得性人类呼吸道感染的常见原因。在细菌向宿主的进化适应过程中，病原体的基因组被大大减少，导致细胞壁丢失，代谢途径受限和毒力因子相对较少。由于与宿主蛋白相互作用，表面暴露的蛋白质（在糖酵解酶，热休克蛋白和伴侣蛋白中）在细胞溶胶定位的代谢和调节过程中起主要作用，被认为是导致发病的原因。在这些月光照下的蛋白质中，某些成员被证实与几种宿主组分结合。肺炎支原体的3-磷酸甘油醛脱氢酶（GAPDH）是这种多结合蛋白的典型例子。为了研究这些相互作用的组织，GAPDH分为四个部分。重组蛋白在大肠杆菌中成功表达，并产生了多克隆抗血清。证实了GAPDH的全长和部分与人A549细胞的结合。此外，几乎所有重组GAPDH蛋白都证明了与人纤溶酶原，玻连蛋白，纤连蛋白和纤维蛋白原的相互作用。在这些蛋白质的存在下，纤溶酶原可被激活为蛋白酶纤溶酶。相反，仅在GAPDH的C末端部分证实了细菌细胞表面的定位。通过使用覆盖该区域的重叠肽，研究的宿主组分与序列^326的结合发现QLVRVVNYCAKL ³³⁷。研究结果表明，GAPDH的表面定位C末端部分在与不同人类蛋白质的结合中起着显著作用，表明其对宿主与病原体相互作用的重要性。