title: Effect of energy metabolism on protein motility in the bacterial outer membrane.
abstract: We demonstrate the energy dependence of the motion of a porin, the lambda-receptor, in the outer membrane of living Escherichia coli by single molecule investigations. By poisoning the bacteria with arsenate and azide, the bacterial energy metabolism was stopped. The motility of individual lambda-receptors significantly and rapidly decreased upon energy depletion. We suggest two different causes for the ceased motility upon comprised energy metabolism: One possible cause is that the cell uses energy to actively wiggle its proteins, this energy being one order-of-magnitude larger than thermal energy. Another possible cause is an induced change in the connection between the lambda-receptor and the membrane structure, for instance by a stiffening of part of the membrane structure. Treatment of the cells with ampicillin, which directly targets the bacterial cell wall by inhibiting cross-linking of the peptidoglycan layer, had an effect similar to energy depletion and the motility of the lambda-receptor significantly decreased. Since the lambda-receptor is closely linked to the peptidoglycan layer, we propose that lambda-receptor motility is directly coupled to the constant and dynamic energy-consuming reconstruction of the peptidoglycan layer. The result of this motion could be to facilitate transport of maltose-dextrins through the porin.
authors.affiliation: The Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Tabita
authors.initials: T
authors.lastname: Winther
authors.forename: Lei
authors.initials: L
authors.lastname: Xu
authors.forename: Kirstine
authors.initials: K
authors.lastname: Berg-Sørensen
authors.forename: Stanley
authors.initials: S
authors.lastname: Brown
authors.forename: Lene B
authors.initials: LB
authors.lastname: Oddershede
mesh_terms: D000465:Algorithms; D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001149:Arsenates / Q000494:pharmacology; D001386:Azides / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D002473:Cell Wall / Q000187:drug effects / Q000502:physiology*; D004734:Energy Metabolism / Q000187:drug effects; D004926:Escherichia coli; D007700:Kinetics; D008954:Models, Biological; D009038:Motion; D010457:Peptidoglycan / Q000378:metabolism; D018272:Porins / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D045663:Quantum Dots; D011991:Receptors, Virus / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001149:Arsenates; D001386:Azides; D001425:Bacterial Outer Membrane Proteins; D010457:Peptidoglycan; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins; D000667:Ampicillin; C025657:arsenic acid