Effect of Energy Metabolism on Protein Motility in the Bacterial Outer Membrane |
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Authors: | Tabita Winther,Kirstine Berg-Sø rensen,Lene B. Oddershede |
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Affiliation: | † The Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark ‡ Department of Physics, Technical University of Denmark, Lyngby, Denmark § Department of Biology, University of Copenhagen, Copenhagen, Denmark |
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Abstract: | We demonstrate the energy dependence of the motion of a porin, the λ-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 λ-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 λ-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 λ-receptor significantly decreased. Since the λ-receptor is closely linked to the peptidoglycan layer, we propose that λ-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. |
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