Control of extracytoplasmic stress responses by regulated intramembrane proteolysis

大肠杆菌σ^E通过胞质外应激诱导的抗σ^E蛋白RseA（一种II型单跨膜蛋白）的两步裂解而活化。我们发现，真核S2P蛋白酶的大肠杆菌同源物RseP（以前的YaeL）作为“RIP（受调节的膜内蛋白水解）”蛋白酶发挥功能，其在DegS在周质侧上的第一次切割之后将第二次“膜内”切割引入抗σ^E蛋白（RseA）。我们的体内和体外结果表明，RseP直接催化RseA的跨膜序列内的蛋白水解。我们还发现，RseP可以切割的跨膜序列的一些模式的膜蛋白是无关的RseA，提供的跨膜区域含有低螺旋倾向的残基。我们现在正在解决的两个步骤的RseA蛋白水解的分子机制和它的调节使用在体外反应系统重建从纯化的组件。

E.coli σ^E is activated by extracytoplasmic stress-induced two step cleavages of the anti-σ^E protein, RseA (a type II single-spanning membrane protein). We showed that RseP (formerly YaeL), an E.coli homolog of the eukaryotic S2P protease, functions as a "RIP(regulated intramembrane proteolysis)" protease that introduces the second "intramembrane" cleavage into anti-σ^E protein (RseA) following the first cleavage on the periplasmic side by DegS. Our in vivo and in vitro results demonstrated that RseP directly catalyzes proteolysis within the transmembrane sequence of RseA. We also found that RseP can cleave transmembrane sequences of some model membrane proteins that are unrelated to RseA, provided that the transmembrane region contains residues of low helical propensity. We are now addressing the molecular mechanisms of the two-step proteolysis of RseA and its regulation using in vitro reaction system reconstituted from purified components.