Secretion of curli fibre subunits is mediated by the outer membrane-localized CsgG protein
Secretion of curli fibre subunits is mediated by the outer membrane-localized CsgG protein
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DOI：
10.1111/j.1365-2958.2005.04997.x
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发表时间：
2006-02-01
影响因子：
3.6
通讯作者：
Chapman, MR
中科院分区：
文献类型：
--
作者：
Robinson, LS;Ashman, EM;Chapman, MR
curli是一种重要的淀粉样蛋白纤维，与生物膜的形成、宿主细胞的粘附和侵袭以及免疫系统的激活有关。CsgA是主要的纤维亚基，CsgE、CsgF和CsgG是参与卷曲生物发生的非结构蛋白。我们已经确定了CsgG在curli亚基跨外膜分泌中的作用。CsgG的定向诱变证实其活性依赖于外膜的定位。纯化的CsgG的旋转阴影电子显微镜显示，该蛋白组装成具有明显中心孔的寡聚复合物。通过共纯化实验确定了低聚的CsgG配合物。抗生素敏感性试验表明，CsgG的过表达使大肠杆菌对抗生素红霉素敏感。在CsgA的n端有一个22个氨基酸的序列，足以引导异源蛋白进入CsgG的分泌器官。最后，我们确定CsgG与另外两个curli组装蛋白CsgE和CsgF参与外膜复合物。
Produced by many Enterobacteriaceae spp., curli are biologically important amyloid fibres that have been associated with biofilm formation, host cell adhesion and invasion, and immune system activation. CsgA is the major fibre subunit and CsgE, CsgF and CsgG are non-structural proteins involved in curli biogenesis. We have characterized the role of CsgG in curli subunit secretion across the outer membrane. Directed mutagenesis of CsgG confirmed that its activity is dependent on localization to the outer membrane. Rotary Shadow electron microscopy of purified CsgG suggested that this protein assembles into an oligomeric complex with an apparent central pore. Oligomeric CsgG complexes were confirmed using co-purification experiments. Antibiotic sensitivity assays demonstrated that overexpression of CsgG rendered Escherichia coli susceptible to the antibiotic erythromycin. A 22-amino-acid sequence at the N-terminus of CsgA was sufficient to direct heterologous proteins to the CsgG secretion apparatus. Finally, we determined that CsgG participates in an outer membrane complex with two other curli assembly proteins, CsgE and CsgF.