Overweg K, Pericone C D, Verhoef G G, Weiser J N, Meiring H D, De Jong A P, De Groot R, Hermans P W
Department of Pediatrics, Sophia Children's Hospital, Erasmus University, Rotterdam, The Netherlands.
Infect Immun. 2000 Aug;68(8):4604-10. doi: 10.1128/IAI.68.8.4604-4610.2000.
Streptococcus pneumoniae undergoes spontaneous phase variation resulting in opaque and transparent colony forms. Differences in colony opacity correlate with differences in virulence: the transparent variants are more capable of colonizing the nasopharynx, whereas the opaque variants show increased virulence during systemic infections. To gain insight into the pathogenesis of pneumococcal disease at the molecular level, protein expression patterns of the phenotypic variants of two pneumococcal strains were compared by high-resolution two-dimensional protein electrophoresis. In comparison with transparent variants, the opaque variants reduced the expression of two proteins and overexpressed one protein. The proteins were identified by mass spectrometric analysis. The protein overexpressed in the opaque phenotype revealed significant homology to elongation factor Ts of Helicobacter pylori. One of the two proteins that were underexpressed in the opaque variants revealed significant homology to the proteinase maturation protein PrtM of Lactocobacillus paracasei, a member of the family of peptidyl-prolyl cis/trans isomerases. A consensus lipoprotein signal sequence suggests that the putative proteinase maturation protein A, designated PpmA, is located at the surface of the pneumococcus and may play a role in the maturation of surface or secreted proteins. The second underexpressed protein was identified as pyruvate oxidase, SpxB. The lower SpxB expression in opaque variants most probably explains the reduced production of hydrogen peroxide, a reaction product of SpxB, in this variant. Since a spxB-defective pneumococcal mutant has decreased ability to colonize the nasopharynx (B. Spellerberg, D. R. Cundell, J. Sandros, B. J. Pearce, I. Idanpaan-Heikkila, C. Rosenow, and H. R. Masure, 1996. Mol. Microbiol. 19:803-813, 1996), our data suggest that SpxB plays an important role in enhancing the ability of transparent variants to efficiently colonize the nasopharynx.
肺炎链球菌会发生自发的相变，产生不透明和透明两种菌落形态。菌落不透明度的差异与毒力差异相关：透明变体更能在鼻咽部定植，而不透明变体在全身感染期间毒力增强。为了在分子水平深入了解肺炎球菌疾病的发病机制，通过高分辨率二维蛋白质电泳比较了两种肺炎球菌菌株表型变体的蛋白质表达模式。与透明变体相比，不透明变体减少了两种蛋白质的表达，并过表达了一种蛋白质。通过质谱分析鉴定了这些蛋白质。在不透明表型中过表达的蛋白质与幽门螺杆菌的延伸因子Ts有显著同源性。在不透明变体中表达下调的两种蛋白质之一与副干酪乳杆菌的蛋白酶成熟蛋白PrtM有显著同源性，PrtM是肽基脯氨酰顺/反异构酶家族的成员。一个共有脂蛋白信号序列表明，假定的蛋白酶成熟蛋白A（命名为PpmA）位于肺炎球菌表面，可能在表面或分泌蛋白的成熟中起作用。第二种表达下调的蛋白质被鉴定为丙酮酸氧化酶SpxB。不透明变体中较低的SpxB表达很可能解释了该变体中SpxB的反应产物过氧化氢产量的降低。由于spxB缺陷的肺炎球菌突变体在鼻咽部定植的能力下降（B. Spellerberg、D. R. Cundell、J. Sandros、B. J. Pearce、I. Idanpaan-Heikkila、C. Rosenow和H. R. Masure，1996. Mol. Microbiol. 19:803 - 813, 1996），我们的数据表明SpxB在增强透明变体有效定植鼻咽部的能力方面起重要作用。
