SurA is a cryptically grooved chaperone that expands unfolded outer membrane proteins
SurA is a cryptically grooved chaperone that expands unfolded outer membrane proteins
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DOI：
10.1073/pnas.2008175117
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发表时间：
2020-10
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通讯作者：
Dagan C. Marx;A. Plummer;Anneliese M. Faustino;Taylor A. Devlin;Michaela A. Roskopf;Mathis J. Leblanc;Henry J. Lessen;B. T. Amann;P. Fleming;S. Krueger;S. Fried;K. Fleming
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作者：
Dagan C. Marx;A. Plummer;Anneliese M. Faustino;Taylor A. Devlin;Michaela A. Roskopf;Mathis J. Leblanc;Henry J. Lessen;B. T. Amann;P. Fleming;S. Krueger;S. Fried;K. Fleming
外膜蛋白在细菌生理学中起着关键作用，并且越来越多地被用作抗生素靶标。SurA是OMP生物发生网络中最重要的伴侣蛋白，被认为通过与BAM复合体相互作用来启动它们的折叠。我们观察到当与SurA结合时，未折叠的外膜蛋白史无前例地扩张。这种扩展提示了一种潜在的机制，通过这种机制，Sura可以将uOMPs运送到BAM复合体。此外，这项研究强调使用整合/杂交结构生物学方法和新兴方法来绘制高度异质性的结构集合，例如与伴侣结合的未折叠蛋白质的结构集成。周质伴侣网络确保细菌外膜蛋白(OMP)的生物发生，最近被确定为抗生素的一个有前途的靶点。SurA是这个网络中最重要的成员，这既是因为它与β-Barrel组装机械复合体的遗传相互作用，也是因为它能够阻止未折叠的omp(UOMP)聚集。仅使用结合能，Sura实现这两个功能的机制还不是很清楚。在这里，我们结合使用光交联、质谱学、溶液散射和分子建模技术来阐明定义苏拉如何溶解uOMPs的关键结构特征。我们的实验数据支持一个模型，即Sura在核心和P1结构域之间形成的凹槽中结合uOMP。这一结合事件导致uOMP其余部分的急剧扩张，这具有许多生物学意义。利用这些实验数据作为约束，我们采用了一种综合建模的方法来创建Sura·uOMP络合物的稀疏模型集。我们使用独立的散射和化学交联数据验证了Sura·uOMP系综的关键结构特征。我们的数据表明，SurA利用三种不同的结合模式与uOMP相互作用，并且一次可以有不止一种SurA与uOMP结合。这项工作表明，与OMP生物发生网络中的其他伴侣相比，SurA以一种独特的方式运作。
Significance Outer membrane proteins play critical roles in bacterial physiology and increasingly are exploited as antibiotic targets. SurA is the most important chaperone in the OMP biogenesis network and is thought to initiate their folding through an interaction with the BAM complex. We observe an unprecedented expansion of unfolded outer membrane proteins when bound to SurA. This expansion suggests a potential mechanism by which SurA can deliver uOMPs to the BAM complex. In addition, this study highlights the use of an integrative/hybrid structural biology approach and emerging methods to map highly heterogeneous structural ensembles, such as that of an unfolded protein bound to a chaperone. The periplasmic chaperone network ensures the biogenesis of bacterial outer membrane proteins (OMPs) and has recently been identified as a promising target for antibiotics. SurA is the most important member of this network, both due to its genetic interaction with the β-barrel assembly machinery complex as well as its ability to prevent unfolded OMP (uOMP) aggregation. Using only binding energy, the mechanism by which SurA carries out these two functions is not well-understood. Here, we use a combination of photo-crosslinking, mass spectrometry, solution scattering, and molecular modeling techniques to elucidate the key structural features that define how SurA solubilizes uOMPs. Our experimental data support a model in which SurA binds uOMPs in a groove formed between the core and P1 domains. This binding event results in a drastic expansion of the rest of the uOMP, which has many biological implications. Using these experimental data as restraints, we adopted an integrative modeling approach to create a sparse ensemble of models of a SurA•uOMP complex. We validated key structural features of the SurA•uOMP ensemble using independent scattering and chemical crosslinking data. Our data suggest that SurA utilizes three distinct binding modes to interact with uOMPs and that more than one SurA can bind a uOMP at a time. This work demonstrates that SurA operates in a distinct fashion compared to other chaperones in the OMP biogenesis network.