Defining the role of the Escherichia coli chaperone SecB using comparative proteomics
Defining the role of the Escherichia coli chaperone SecB using comparative proteomics
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DOI：
10.1074/jbc.m509929200
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发表时间：
2006-04-14
影响因子：
4.8
通讯作者：
de Gier, JW
中科院分区：
文献类型：
--
作者：
Baars, L;Ytterberg, AJ;de Gier, JW
为了更好地理解和识别大肠杆菌胞质伴侣SecB的新底物，我们使用比较蛋白质组学分析了secB无效突变体。secB无效突变不影响细胞生长，但在蛋白质组水平上引起显着差异。在SecB的情况下，动态蛋白质聚集体主要含有分泌蛋白质积累在细胞质中。在放射性标记的全细胞裂解物中检测到未加工的分泌蛋白。此外，组装的大部分外膜蛋白质组减慢，而其稳态组成几乎没有受到影响。响应于分泌蛋白的聚集和延迟分选，细胞质伴侣DnaK、GroEL/ES、Clp B、IbpA/B和HslU上调数倍，最有可能在其延迟易位期间稳定分泌蛋白和/或拯救聚集的分泌蛋白。通过“经典”脉冲标记实验证实了受secB无效突变影响的12种分泌蛋白（DegP、FhuA、FkpA、OmpT、OmpX、OppA、TolB、TolC、YbgF、YcgK、YgiW和YncE）的SecB/A依赖性。我们的研究增加了三倍以上的已知SecB依赖性分泌蛋白的数量，并表明SecB的主要作用是促进分泌蛋白靶向Sec-translocase。
To improve understanding and identify novel substrates of the cytoplasmic chaperone SecB in Escherichia coli, we analyzed a secB null mutant using comparative proteomics. The secB null mutation did not affect cell growth but caused significant differences at the proteome level. In the absence of SecB, dynamic protein aggregates containing predominantly secretory proteins accumulated in the cytoplasm. Unprocessed secretory proteins were detected in radiolabeled whole cell lysates. Furthermore, the assembly of a large fraction of the outer membrane proteome was slowed down, whereas its steady state composition was hardly affected. In response to aggregation and delayed sorting of secretory proteins, cytoplasmic chaperones DnaK, GroEL/ES, ClpB, IbpA/B, and HslU were up-regulated severalfold, most likely to stabilize secretory proteins during their delayed translocation and/or rescue aggregated secretory proteins. The SecB/A dependence of 12 secretory proteins affected by the secB null mutation ( DegP, FhuA, FkpA, OmpT, OmpX, OppA, TolB, TolC, YbgF, YcgK, YgiW, and YncE) was confirmed by "classical" pulse-labeling experiments. Our study more than triples the number of known SecB-dependent secretory proteins and shows that the primary role of SecB is to facilitate the targeting of secretory proteins to the Sec-translocase.