The DsbA signal sequence directs efficient, cotranslational export of passenger proteins to the Escherichia coli periplasm via the signal recognition particle pathway
The DsbA signal sequence directs efficient, cotranslational export of passenger proteins to the Escherichia coli periplasm via the signal recognition particle pathway
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DOI：
10.1128/jb.185.19.5706-5713.2003
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发表时间：
2003-10-01
影响因子：
3.2
通讯作者：
Beckwith, J
中科院分区：
文献类型：
--
作者：
Schierle, CF;Berkmen, M;Beckwith, J
大肠杆菌胞质蛋白硫氧还蛋白1可以通过DsbA蛋白（DsbAss）的信号序列有效地输出到胞质周围空间，而不能通过碱性磷酸酶（PhoA）或麦芽糖结合蛋白（MBP）的信号序列输出。利用信号识别粒子（SRP）通路的突变，我们发现DsbAss将硫氧还蛋白1引导至SRP输出通路。当DsbAss与MBP融合时，MBP也被定向到SRP通路。我们直接表明，与使用本地信号序列时的MBP输出模式相比，dsbas促进的MBP输出在很大程度上是共平移的。然而，无论是DsbAss对硫氧还蛋白1的输出，还是DsbA自身对SecA的轻微抑制都非常敏感。这些结果表明SecA可能在缓慢的翻译后途径和依赖srp的共翻译途径中都是必不可少的。最后，可能是因为其在细胞质中的快速折叠，硫氧还蛋白与基因融合方法一起，为利用SRP途径的信号序列提供了一个敏感的分析系统。
The Escherichia coli cytoplasmic protein thioredoxin 1 can be efficiently exported to the periplasmic space by the signal sequence of the DsbA protein (DsbAss) but not by the signal sequence of alkaline phosphatase (PhoA) or maltose binding protein (MBP). Using mutations of the signal recognition particle (SRP) pathway, we found that DsbAss directs thioredoxin 1 to the SRP export pathway. When DsbAss is fused to MBP, MBP also is directed to the SRP pathway. We show directly that the DsbAss-promoted export of MBP is largely cotranslational, in contrast to the mode of MBP export when the native signal sequence is utilized. However, both the export of thioredoxin 1 by DsbAss and the export of DsbA itself are quite sensitive to even the slight inhibition of SecA. These results suggest that SecA may be essential for both the slow posttranslational pathway and the SRP-dependent cotranslational pathway. Finally, probably because of its rapid folding in the cytoplasm, thioredoxin provides, along with gene fusion approaches, a sensitive assay system for signal sequences that utilize the SRP pathway.