Department of Biological Sciences, Ohio University, Athens, Ohio, USA.
Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida, USA.
J Bacteriol. 2021 Mar 8;203(7). doi: 10.1128/JB.00681-20.
Peptidyl-prolyl isomerases (PPIases) are enzymes that assist in protein folding around proline-peptide bonds, and they often possess chaperone activity. encodes three PPIases, i.e., PrsA, PpiB, and trigger factor (TF). Previous work by our group demonstrated a role for both PrsA and PpiB in ; however, TF remains largely unstudied. Here, we identify a role for TF in biofilm formation and demonstrate cooperation between TF and the cytoplasmic PPIase PpiB. Mutation of the gene (encoding TF) led to reduced biofilm development but no significant attenuation of virulence in a mouse model of infection. To investigate whether TF possesses chaperone activity, we analyzed the ability of a mutant to survive acid and base stress. While there was no significant decrease for a mutant, a double mutant exhibited significant decreases in cell viability after acid and base challenges. We then demonstrated that a double mutant had exacerbated phenotypes and , compared to either single mutant. Finally, immunoprecipitation of epitope-tagged PpiB revealed that PpiB interacted with 4 times the number of proteins when TF was absent from the cell, suggesting that it may be compensating for the loss of TF. Interestingly, the only proteins found to interact with TF were TF itself, fibronectin-binding protein B (FnBPB), and the chaperone protein ClpB. Collectively, these results support the first phenotype for TF and demonstrate a greater network of cooperation between chaperone proteins in encodes a large number of virulence factors that aid the bacterium in survival and pathogenesis. These virulence factors have a wide variety of functions; however, they must all be properly secreted in order to be functional. Bacterial chaperone proteins often assist in secretion by trafficking proteins to secretion machinery or assisting in proper protein folding. Here, we report that the chaperone TF contributes to biofilm formation and cooperates with the chaperone PpiB to regulate virulence processes. These data highlight the first known role for TF in and suggest that chaperone proteins may be involved in a greater regulatory network in the cell.
肽基脯氨酰顺反异构酶（PPIases）是一类能够辅助脯氨酸-肽键周围蛋白质折叠的酶，它们通常具有分子伴侣活性。编码三种 PPIases，即 PrsA、PpiB 和触发因子（TF）。我们之前的研究表明，PrsA 和 PpiB 在 中均发挥作用；然而，TF 仍在很大程度上未被研究。在这里，我们鉴定了 TF 在 生物膜形成中的作用，并证明了 TF 与细胞质 PPIase PpiB 之间的合作。突变 基因（编码 TF）导致生物膜发育减少，但在感染小鼠模型中对毒力没有显著减弱。为了研究 TF 是否具有分子伴侣活性，我们分析了 突变体在酸和碱胁迫下的生存能力。虽然 突变体没有明显减少，但 双突变体在酸和碱挑战后细胞活力明显下降。然后我们证明了与任一单突变体相比， 双突变体的表型都明显加重 。最后，用表位标记的 PpiB 进行免疫沉淀，发现当细胞中没有 TF 时，PpiB 与蛋白的相互作用增加了 4 倍，这表明它可能在弥补 TF 的缺失。有趣的是，与 TF 相互作用的唯一蛋白是 TF 本身、纤维连接蛋白结合蛋白 B（FnBPB）和伴侣蛋白 ClpB。总之，这些结果支持了 基因 TF 的第一个表型，并证明了在 中伴侣蛋白之间存在更大的合作网络。编码大量毒力因子，这些因子有助于细菌的存活和发病机制。这些毒力因子具有广泛的功能；然而，它们都必须正确分泌才能发挥功能。细菌伴侣蛋白通常通过将蛋白运送到分泌机制或协助正确折叠来协助分泌。在这里，我们报告 伴侣蛋白 TF 有助于生物膜形成，并与伴侣蛋白 PpiB 合作调节 毒力过程。这些数据突出了 TF 在 中的第一个已知作用，并表明 伴侣蛋白可能参与细胞中更大的调控网络。
