Driessen A J
Department of Microbiology, University of Groningen, Haren, The Netherlands.
EMBO J. 1992 Mar;11(3):847-53. doi: 10.1002/j.1460-2075.1992.tb05122.x.
The SecY/E protein of Escherichia coli was coreconstituted with the proton pump bacteriorhodopsin and cytochrome c oxidase yielding proteoliposomes capable of sustaining a protonmotive force (delta p) of defined polarity and composition. Proteoliposomes support the ATP- and SecA-dependent translocation of proOmpA which is stimulated by a delta p, inside acid and positive. delta p of opposite polarity, inside alkaline and negative, suppresses translocation while SecA-mediated ATP hydrolysis continues unabated. delta psi and delta pH are equally effective in promoting or inhibiting translocation. Membrane-spanning translocation intermediates move backwards in the presence of a reversed delta p. These results support a model [Schiebel, E., Driessen, A.J.M., Hartl, F.-U. and Wickner, W. (1991) Cell, 64, 927-939] in which the delta p defines the direction of translocation after ATP hydrolysis has released proOmpA from its association with SecA. The polarity effect of the delta p challenges models involving delta p-dependent membrane destabilization and provides further evidence for a role of the delta p as driving force in precursor protein translocation.
大肠杆菌的SecY/E蛋白与质子泵细菌视紫红质和细胞色素c氧化酶共同重建，产生了能够维持具有特定极性和组成的质子动力（Δp）的蛋白脂质体。蛋白脂质体支持前体外膜蛋白A（proOmpA）依赖ATP和SecA的易位，该易位受到Δp的刺激，Δp为内部酸性且为正。相反极性的Δp，即内部碱性且为负，则会抑制易位，而SecA介导的ATP水解仍会持续进行。膜电位差（Δψ）和pH梯度（ΔpH）在促进或抑制易位方面同样有效。在反向Δp存在的情况下，跨膜易位中间体向后移动。这些结果支持了一个模型[Schiebel, E., Driessen, A.J.M., Hartl, F.-U.和Wickner, W. (1991) Cell, 64, 927 - 939]，其中在ATP水解使proOmpA从与SecA的结合中释放后，Δp定义了易位的方向。Δp的极性效应挑战了涉及Δp依赖性膜去稳定化的模型，并为Δp作为前体蛋白易位驱动力的作用提供了进一步的证据。
