Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
Structure. 2012 Jul 3;20(7):1154-66. doi: 10.1016/j.str.2012.04.014. Epub 2012 May 31.
Escherichia coli export the protein YebF into the extracellular medium by a two-step process. However, as no general outer membrane protein secretion system common to all E. coli strains has been reported, the mechanism of export has remained unclear. Herein, we identify the outer membrane proteins OmpF, OmpC, and OmpX as central to the YebF export mechanism using both genetic and planar lipid bilayer experiments. The nuclear magnetic resonance structural ensemble of YebF reveals a cystatin-like fold consisting of a structured core and an extended dynamic surface in a state of conformational exchange. This surface, conserved throughout YebF orthologs of Enterobacteriaceae, may facilitate the porin-mediated transport of YebF as amino acid substitutions of dynamic residues reduced secretion to the extracellular medium. Our results demonstrate that OmpF and OmpC not only operate to import ions and protein toxins but may also contribute to the export of the YebF protein family.
大肠杆菌通过两步过程将蛋白质 YebF 输出到细胞外培养基中。然而，由于尚未报道所有大肠杆菌菌株都普遍存在的通用外膜蛋白分泌系统，因此其输出机制仍不清楚。在此，我们使用遗传和平面脂质双层实验确定了外膜蛋白 OmpF、OmpC 和 OmpX 是 YebF 输出机制的核心。YebF 的核磁共振结构集合揭示了一种类似于半胱氨酸蛋白酶抑制剂的折叠结构，由一个结构核心和一个处于构象交换状态的扩展动态表面组成。这种表面在肠杆菌科的 YebF 同源物中是保守的，可能有助于 YebF 的孔道介导运输，因为动态残基的取代会减少氨基酸向细胞外培养基的分泌。我们的结果表明，OmpF 和 OmpC 不仅用于导入离子和蛋白毒素，还可能有助于 YebF 蛋白家族的输出。
