Bacterial cell envelope protein (CEP) complexes mediate a range of processes, including membrane assembly, antibiotic resistance and metabolic coordination. However, only limited characterization of relevant macromolecules has been reported to date. Here we present a proteomic survey of 1,347 CEPs encompassing 90% inner- and outer-membrane and periplasmic proteins of Escherichia coli. After extraction with non-denaturing detergents, we affinity-purified 785 endogenously tagged CEPs and identified stably associated polypeptides by precision mass spectrometry. The resulting high-quality physical interaction network, comprising 77% of targeted CEPs, revealed many previously uncharacterized heteromeric complexes. We found that the secretion of autotransporters requires translocation and the assembly module TamB to nucleate proper folding from periplasm to cell surface through a cooperative mechanism involving the β-barrel assembly machinery. We also establish that an ABC transporter of unknown function, YadH, together with the Mla system preserves outer membrane lipid asymmetry. This E. coli CEP 'interactome' provides insights into the functional landscape governing CE systems essential to bacterial growth, metabolism and drug resistance.

中文翻译：

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大肠杆菌中细胞包膜蛋白复合物的全球格局。

细菌细胞包膜蛋白（CEP）复合物介导一系列过程，包括膜组装，抗生素抗性和代谢协调。然而，迄今为止，仅报道了有关大分子的有限表征。在这里，我们对1,347个CEP进行了蛋白质组学调查，其中涵盖了90％的大肠杆菌内膜和外膜以及周质蛋白。用非变性去污剂提取后，我们亲和纯化了785个内源标记的CEP，并通过精密质谱法鉴定了稳定相关的多肽。由此产生的高质量物理相互作用网络（包含77％的目标CEP）揭示了许多以前未表征的异聚复合物。我们发现自转运蛋白的分泌需要易位，组装模块TamB通过涉及β-桶组装机械的协同机制使从周质到细胞表面的适当折叠成核。我们还建立了未知功能的YabH ABC转运蛋白与Mla系统一起保留了外膜脂质不对称性。此大肠杆菌CEP“相互作用组”提供了对控制细菌生长，代谢和耐药性必不可少的CE系统的功能格局的见解。