Dunstan Rhys A, Hay Iain D, Wilksch Jonathan J, Schittenhelm Ralf B, Purcell Anthony W, Clark Joan, Costin Adam, Ramm Georg, Strugnell Richard A, Lithgow Trevor
Department of Microbiology, Monash University, Clayton, Vic., 3800, Australia.
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Vic., 3800, Australia.
Mol Microbiol. 2015 Aug;97(4):616-29. doi: 10.1111/mmi.13055. Epub 2015 Jun 6.
In Gram-negative bacteria, β-barrel proteins are integrated into the outer membrane by the β-barrel assembly machinery, with key components of the machinery being the Omp85 family members BamA and TamA. Recent crystal structures and cryo-electron microscopy show a diverse set of secretion pores in Gram-negative bacteria, with α-helix (Wza and GspD) or β-strand (CsgG) transmembrane segments in the outer membrane. We developed assays to measure the assembly of three distinct secretion pores that mediate protein (GspD), curli fibre (CsgG) and capsular polysaccharide (Wza) secretion by bacteria and show that depletion of BamA and TamA does not diminish the assembly of Wza, GspD or CsgG. Like the well characterised pilotins for GspD and other secretins, small periplasmic proteins enhance the assembly of the CsgG β-barrel. We discuss a model for integral protein assembly into the bacterial outer membrane, focusing on the commonalities and differences in the assembly of Wza, GspD and CsgG.
在革兰氏阴性菌中，β-桶状蛋白通过β-桶状组装机制整合到外膜中，该机制的关键组分是Omp85家族成员BamA和TamA。最近的晶体结构和冷冻电子显微镜显示革兰氏阴性菌中有多种分泌孔，在外膜中有α-螺旋（Wza和GspD）或β-链（CsgG）跨膜片段。我们开发了检测方法来测量三种不同分泌孔的组装情况，这些分泌孔介导细菌分泌蛋白质（GspD）、卷曲纤维（CsgG）和荚膜多糖（Wza），结果表明BamA和TamA的缺失不会减少Wza、GspD或CsgG的组装。与已充分表征的GspD和其他分泌素的先导肽一样，小的周质蛋白会增强CsgGβ-桶的组装。我们讨论了一个将整合蛋白组装到细菌外膜中的模型，重点关注Wza、GspD和CsgG组装过程中的共性和差异。
