Cezairliyan Brent O, Sauer Robert T
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139.
Proc Natl Acad Sci U S A. 2007 Mar 6;104(10):3771-6. doi: 10.1073/pnas.0611567104. Epub 2007 Feb 26.
The Escherichia coli envelope-stress response is a sensor system that increases transcription of stress genes in the cytoplasm when misfolded porins are detected in the periplasm. This response is initiated by DegS cleavage of the periplasmic domain of RseA, a transmembrane protein. Additional proteolysis of transmembrane and cytoplasmic portions of RseA then frees the sigma(E) transcription factor, which directs the transcriptional response. We show that RseB protein, a known negative regulator, inhibits proteolysis by DegS in vitro by binding tightly to the periplasmic domain of RseA. Inhibition of DegS cleavage requires RseB binding to a conserved region near the C terminus of the poorly structured RseA domain, but the RseA sequences that mediate DegS recognition and RseB binding do not overlap directly. Although DegS cleavage of RseA is normally activated by binding of the C termini of porins to the PDZ domain of DegS, RseB inhibition is independent of this activation mechanism.
大肠杆菌包膜应激反应是一种传感系统，当在周质中检测到错误折叠的孔蛋白时，该系统会增加细胞质中应激基因的转录。这种反应由跨膜蛋白RseA周质结构域的DegS切割引发。RseA跨膜和细胞质部分的进一步蛋白水解随后释放出σ(E)转录因子，该因子指导转录反应。我们发现，已知的负调节因子RseB蛋白通过紧密结合RseA的周质结构域在体外抑制DegS的蛋白水解作用。DegS切割的抑制需要RseB与结构松散的RseA结构域C末端附近的保守区域结合，但介导DegS识别和RseB结合的RseA序列并不直接重叠。尽管RseA的DegS切割通常通过孔蛋白的C末端与DegS的PDZ结构域结合来激活，但RseB的抑制作用与这种激活机制无关。
