title: Interactions of the energy transducer TonB with noncognate energy-harvesting complexes.
abstract: The TonB and TolA proteins are energy transducers that couple the ion electrochemical potential of the cytoplasmic membrane to support energy-dependent processes at the outer membrane of the gram-negative envelope. The transfer of energy to these transducers is facilitated by energy-harvesting complexes, which are heteromultimers of cytoplasmic membrane proteins with homologies to proton pump proteins of the flagellar motor. Although the cognate energy-harvesting complex best services each transducer, components of the complexes (for TonB, ExbB and ExbD; for TolA, TolQ and TolR) are sufficiently similar that each complex can imperfectly replace the other. Previous investigations of this molecular cross talk considered energy-harvesting complex components expressed from multicopy plasmids in strains in which the corresponding genes were interrupted by insertions, partially absent due to polarity, or missing due to a larger deletion. These questions were reexamined here using strains in which individual genes were removed by precise deletions and, where possible, components were expressed from single-copy genes with native promoters. By more closely approximating natural stoichiometries between components, this study provided insight into the roles of energy-harvesting complexes in both the energization and the stabilization of TonB. Further, the data suggest a distinct role for ExbD in the TonB energy transduction cycle.
authors.affiliation: Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
authors.forename: Kerry K
authors.initials: KK
authors.lastname: Brinkman
authors.forename: Ray A
authors.initials: RA
authors.lastname: Larsen
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004734:Energy Metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010743:Phospholipids / Q000502:physiology; D010957:Plasmids; D017384:Sequence Deletion
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010743:Phospholipids; C062093:tolA protein, E coli; C057616:tonB protein, Bacteria; C060792:tolQ protein, E coli