title: Precursor protein translocation by the Escherichia coli translocase is directed by the protonmotive force.
abstract: 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.
authors.affiliation: Department of Microbiology, University of Groningen, Haren, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Driessen
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001692:Biological Transport; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D008715:Methionine / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D011522:Protons; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011498:Protein Precursors; D011522:Protons; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; C057841:SecY protein, E coli; C057184:outer membrane protein A precursor (E coli); D000255:Adenosine Triphosphate; D008715:Methionine; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins