Schiebel E, Wickner W
Molecular Biology Institute, University of California, Los Angeles 90024-1570.
J Biol Chem. 1992 Apr 15;267(11):7505-10.
The electrochemical potential drives the translocation of the precursor form of outer membrane protein A (proOmpA) and other proteins across the plasma membrane of Escherichia coli. We have measured the electrical potential, delta psi, across inverted membrane vesicles during proOmpA translocation. delta psi, generated by the electron transport chain, is substantially dissipated by proOmpA translocation. delta psi dissipation requires SecA, ATP, and proOmpA. proOmpA which, due to the covalent addition of a folded protein to a cysteinyl side chain, is arrested during its translocation, can nevertheless cause the loss of delta psi. Thus the movement of charged amino acyl residues is not dissipating the potential. This translocation-specific reduction in delta psi is only seen in the presence of halide anions, although halide anions are not needed for proOmpA translocation per se. We therefore propose that translocation intermediates directly increase the membrane permeability to halide anions.
电化学势驱动外膜蛋白A（proOmpA）的前体形式及其他蛋白质穿过大肠杆菌的质膜。我们在proOmpA转运过程中测量了跨内膜囊泡的电势差（Δψ）。由电子传递链产生的Δψ会因proOmpA的转运而大幅耗散。Δψ的耗散需要SecA、ATP和proOmpA。尽管由于折叠蛋白共价添加到半胱氨酸侧链上，proOmpA在转运过程中受阻，但它仍会导致Δψ的丧失。因此，带电荷的氨酰基残基的移动并没有耗散电势。这种转运特异性的Δψ降低仅在卤化物阴离子存在时才会出现，尽管卤化物阴离子本身并非proOmpA转运所必需。因此，我们提出转运中间体直接增加了膜对卤化物阴离子的通透性。
