Abstract
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.
Highlights
The electrochemical potentialdrives the transloca- domain, the SecA protein, which is bound to the membrane tion of the precursor form of outer membrane protein via its affinities for acidic phospholipids
We propose that translocation and for the leader and maturedomains of the preprotein (Lill et al, 1990).ATP binding causes an initial transfer of a loop of the protein across the membrane (Schiebel et al, 1991).Upon nucleotide hydrolysis, proOmpA is released from tight SecA association and canundergo a rapid completion of translocation, driven by both AI) and ApH (Schiebel et al, 1991)
Rather than finding creas trypsin inhibitor to proOmpA at cysteine 290 or 302,cross- such dissipation of potential by a transitingpolypeptide chain, linked by N-succinimidyl-3-(2-pyridyldithio)-propiona(tSePDP);ox- we report that translocation intermediates, even when onol VI, bis(3-propyl-5-oxoisoxazol-4-yl)pentamethionxeonol; BSA, bovine serum albumin; DTT, dithiothreitol; SDS, sodium dodecyl sulfate; PAGE, polyacrylamidegel electrophoresis; HEPES, 4-(2
Summary
The electrochemical potentialdrives the transloca- domain, the SecA protein, which is bound to the membrane tion of the precursor form of outer membrane protein via its affinities for acidic phospholipids A (proOmpA)andother proteinsacrosstheplasma Hendrick and Wickner, 1991) and for the SecY/E integral membrane of Escherichia coli.We have measured the membrane protein. The latter is comprised of three compoelectricalpotential,Art, across invertedmembraneves- nents, the SecY and SecE polypeptides and one polypeptide icles during proOmpA translocation.A#, generated by of as yet unidentified gene or function (Brundage et al, 1990). We propose that translocation and for the leader and maturedomains of the preprotein (Lill et al, 1990).ATP binding causes an initial transfer of a loop of the protein across the membrane (Schiebel et al., 1991).Upon nucleotide hydrolysis, proOmpA is released from tight SecA association and canundergo a rapid completion of translocation, driven by both AI) and ApH (Schiebel et al, 1991).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
