title: Proton transfer is rate-limiting for translocation of precursor proteins by the Escherichia coli translocase.
abstract: The protonmotive force stimulates translocation in vivo, in crude in vitro reactions, and in a purified, reconstituted reaction. Translocation activity is a function of the pH at the inner face of the membrane. Both the transmembrane pH gradient and the transmembrane electrical potential stimulate translocation. A late-stage translocation intermediate of the proOmpA preprotein completes its translocation in the absence of ATP when a protonmotive force is imposed. This completion of translocation is retarded by a factor of greater than 3 in deuterium oxide relative to water, demonstrating that translocation involves proton-transfer reactions in rate-limiting steps.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles 90024-1737.
authors.forename: A J
authors.initials: AJ
authors.lastname: Driessen
authors.forename: W
authors.initials: W
authors.lastname: Wickner
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials; D026901:Membrane Transport Proteins; D009243:NAD / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D011498:Protein Precursors; D000069816:SEC Translocation Channels; C057184:outer membrane protein A precursor (E coli); D009243:NAD; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins