Swanson Kena A, Taylor Lacey D, Frank Shaun D, Sturdevant Gail L, Fischer Elizabeth R, Carlson John H, Whitmire William M, Caldwell Harlan D
Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th St., Hamilton, MT 59840, USA.
Infect Immun. 2009 Jan;77(1):508-16. doi: 10.1128/IAI.01173-08. Epub 2008 Nov 10.
Chlamydia trachomatis is a globally important obligate intracellular bacterial pathogen that is a leading cause of sexually transmitted disease and blinding trachoma. Effective control of these diseases will likely require a preventative vaccine. C. trachomatis polymorphic membrane protein D (PmpD) is an attractive vaccine candidate as it is conserved among C. trachomatis strains and is a target of broadly cross-reactive neutralizing antibodies. We show here that immunoaffinity-purified native PmpD exists as an oligomer with a distinct 23-nm flower-like structure. Two-dimensional blue native-sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses showed that the oligomers were composed of full-length PmpD (p155) and two proteolytically processed fragments, the p73 passenger domain (PD) and the p82 translocator domain. We also show that PmpD undergoes an infection-dependent proteolytic processing step late in the growth cycle that yields a soluble extended PD (p111) that was processed into a p73 PD and a novel p30 fragment. Interestingly, soluble PmpD peptides possess putative eukaryote-interacting functional motifs, implying potential secondary functions within or distal to infected cells. Collectively, our findings show that PmpD exists as two distinct forms, a surface-associated oligomer exhibiting a higher-order flower-like structure and a soluble form restricted to infected cells. We hypothesize that PmpD is a multifunctional virulence factor important in chlamydial pathogenesis and could represent novel vaccine or drug targets for the control of human chlamydial infections.
沙眼衣原体是一种在全球范围内具有重要意义的专性细胞内细菌病原体，是性传播疾病和致盲性沙眼的主要病因。有效控制这些疾病可能需要一种预防性疫苗。沙眼衣原体多态性膜蛋白D（PmpD）是一种有吸引力的疫苗候选物，因为它在沙眼衣原体菌株中保守，并且是广泛交叉反应性中和抗体的靶点。我们在此表明，免疫亲和纯化的天然PmpD以具有独特23纳米花状结构的寡聚体形式存在。二维蓝色天然十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析表明，这些寡聚体由全长PmpD（p155）以及两个经蛋白水解加工的片段组成，即p73乘客结构域（PD）和p82转运结构域。我们还表明，PmpD在生长周期后期经历一个依赖感染的蛋白水解加工步骤，产生一种可溶的延伸PD（p111），该延伸PD被加工成p73 PD和一个新的p30片段。有趣的是，可溶性PmpD肽具有假定的与真核生物相互作用的功能基序，这意味着在感染细胞内或细胞外可能具有潜在的二级功能。总的来说，我们的研究结果表明，PmpD以两种不同的形式存在，一种是表面相关的寡聚体，呈现出高阶花状结构，另一种是仅限于感染细胞的可溶形式。我们推测，PmpD是沙眼衣原体发病机制中一种重要的多功能毒力因子，可能代表控制人类沙眼衣原体感染的新型疫苗或药物靶点。
