Bigot Armelle, Botton Eleonore, Dubail Iharilalao, Charbit Alain
INSERM U-570, CHU Necker-Enfants Malades, 156, rue de Vaugirard, 75730 Paris Cedex 15, France.
Appl Environ Microbiol. 2006 Oct;72(10):6623-31. doi: 10.1128/AEM.00624-06.
Molecular chaperones play an essential role in the folding of nascent chain polypeptides, as well as in the refolding and degradation of misfolded or aggregated proteins. They also assist in protein translocation and participate in stress functions. We identified a gene, designated tig, encoding a protein homologous to trigger factor (TF), a cytosolic ribosome-associated chaperone, in the genome of Listeria monocytogenes. We constructed a chromosomal Delta tig deletion and evaluated the impact of the mutation on bacterial growth in broth under various stress conditions and on pathogenesis. The Delta tig deletion did not affect cell viability but impaired survival in the presence of heat and ethanol stresses. We also identified the ffh gene, encoding a protein homologous to the SRP54 eukaryotic component of the signal recognition particle. However, a Delta ffh deletion was not tolerated, suggesting that Ffh is essential, as it is in Bacillus subtilis and Escherichia coli. Thus, although dispensable for growth, TF is involved in the stress response of L. monocytogenes. The Delta tig mutant showed no or very modest intracellular survival defects in eukaryotic cells. However, in vivo it showed a reduced capacity to persist in the spleens and livers of infected mice, revealing that TF has a role in the pathogenicity of L. monocytogenes.
分子伴侣在新生链多肽的折叠过程中发挥着重要作用，同时也参与错误折叠或聚集蛋白的重折叠和降解。它们还协助蛋白质转运并参与应激功能。我们在单核细胞增生李斯特菌的基因组中鉴定出一个名为tig的基因，该基因编码一种与触发因子（TF）同源的蛋白质，触发因子是一种与胞质核糖体相关的伴侣蛋白。我们构建了一个染色体Δtig缺失突变体，并评估了该突变对细菌在各种应激条件下在肉汤中的生长以及对致病性的影响。Δtig缺失并不影响细胞活力，但在热应激和乙醇应激条件下会损害细菌的存活能力。我们还鉴定出了ffh基因，该基因编码一种与信号识别颗粒的真核组分SRP54同源的蛋白质。然而，Δffh缺失突变体无法存活，这表明Ffh与枯草芽孢杆菌和大肠杆菌中的情况一样，是必不可少的。因此，尽管TF对于生长并非必需，但它参与了单核细胞增生李斯特菌的应激反应。Δtig突变体在真核细胞中未表现出或仅表现出非常轻微的细胞内存活缺陷。然而，在体内，它在感染小鼠的脾脏和肝脏中持续存在的能力降低，这表明TF在单核细胞增生李斯特菌的致病性中发挥作用。
