Heat and pressure resistance relates to protein folding and aggregation

The locus of heat resistance (LHR) confers extreme heat resistance in E. coli. This study explored the role of the LHR in pressure resistance of E. coli, as well as its relationship with protein folding and aggregation in vivo. The role of LHR was investigated in E. coli MG1655 expressing a ibpA-yfp fusion. The expression of proteins by the LHR was determined by mass spectrometry based proteomics; inclusion bodies of untreated and treated cells were also analysed by proteomics, and by observation with fluorescence microscope. In total, 11 proteins of LHR were expressed, including sHSP20, ClpKGI, sHSP, YdfX1 and YdfX2, HdeD, KefB, Trx, PsiE, DegP, and a hypothetical proteins. The proteomic analysis of inclusion bodies revealed a differential abundance of proteins related to oxidative stress in strains carrying the LHR. The LHR reduced the presence of inclusion bodies after heat or pressure treatment, indicating that proteins expressed by the LHR prevent or reverse protein aggregation. The phenotype of the LHR was also mediated by the expression of a fragment containing only sHSP20, ClpKGI, sHSP. The LHR and the fragment encoding only for sHSP20, ClpKGI, sHSP also enhanced pressure resistance in E. coli MG1655 but had no effect on pressure resistance of E. coli LMM1010. In conclusion, the LHR confers pressure resistance to some strains of E. coli, and reduces protein aggregation. Pressure and heat resistance, however, are also dependent on additional LHR-encoded functions.

耐热基因座（locus of heat resistance, LHR）可赋予大肠杆菌（E. coli）极强的耐热性。本研究探讨了LHR在大肠杆菌耐压性调控中的作用，以及其与体内蛋白质折叠和聚集过程的关联。本研究以表达ibpA-yfp融合基因（ibpA-yfp fusion）的大肠杆菌MG1655为研究对象，探究了LHR的生物学功能。通过基于质谱的蛋白质组学（mass spectrometry based proteomics）分析了LHR编码的蛋白质表达谱；同时对未处理与经处理的细胞包涵体开展蛋白质组学分析，并借助荧光显微镜（fluorescence microscope）进行形态观察。共计鉴定得到11种由LHR编码表达的蛋白质，包括小热休克蛋白20（sHSP20）、ClpKGI、小热休克蛋白（sHSP）、YdfX1、YdfX2、HdeD、KefB、Trx、PsiE、DegP以及一种假设蛋白（hypothetical protein）。包涵体蛋白质组学分析显示，携带LHR的菌株中，与氧化应激（oxidative stress）相关的蛋白质丰度存在显著差异。LHR可降低热或压力处理后细胞内包涵体的数量，提示LHR编码的蛋白质能够阻止或逆转蛋白质聚集（protein aggregation）过程。LHR的功能表型还可通过仅包含sHSP20、ClpKGI与sHSP的基因片段的表达得以介导。LHR以及仅编码sHSP20、ClpKGI与sHSP的基因片段，均可增强大肠杆菌MG1655的耐压性，但对大肠杆菌LMM1010的耐压性无显著影响。综上，LHR可赋予部分大肠杆菌菌株耐压性，并抑制蛋白质聚集。不过，耐压性与耐热性的实现同时还依赖于LHR编码的其他额外功能蛋白。