title: High hydrostatic pressure induces counterclockwise to clockwise reversals of the Escherichia coli flagellar motor.
abstract: The bacterial flagellar motor is a reversible rotary machine that rotates a left-handed helical filament, allowing bacteria to swim toward a more favorable environment. The direction of rotation reverses from counterclockwise (CCW) to clockwise (CW), and vice versa, in response to input from the chemotaxis signaling circuit. CW rotation is normally caused by binding of the phosphorylated response regulator CheY (CheY-P), and strains lacking CheY are typically locked in CCW rotation. The detailed mechanism of switching remains unresolved because it is technically difficult to regulate the level of CheY-P within the concentration range that produces flagellar reversals. Here, we demonstrate that high hydrostatic pressure can induce CW rotation even in the absence of CheY-P. The rotation of single flagellar motors in Escherichia coli cells with the cheY gene deleted was monitored at various pressures and temperatures. Application of >120 MPa pressure induced a reversal from CCW to CW at 20°C, although at that temperature, no motor rotated CW at ambient pressure (0.1 MPa). At lower temperatures, pressure-induced changes in direction were observed at pressures of <120 MPa. CW rotation increased with pressure in a sigmoidal fashion, as it does in response to increasing concentrations of CheY-P. Application of pressure generally promotes the formation of clusters of ordered water molecules on the surfaces of proteins. It is possible that hydration of the switch complex at high pressure induces structural changes similar to those caused by the binding of CheY-P.
authors: The Hakubi Center for Advanced Research, Kyoto University, Kyoto, Japan. mnishiyama@icems.kyoto-u.ac.jp
authors: Masayoshi
authors: M
authors: Nishiyama
authors: Yoshiyuki
authors: Y
authors: Sowa
authors: Yoshifumi
authors: Y
authors: Kimura
authors: Michio
authors: M
authors: Homma
authors: Akihiko
authors: A
authors: Ishijima
authors: Masahide
authors: M
authors: Terazima
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001696:Biomechanical Phenomena; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D005407:Flagella / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006874:Hydrostatic Pressure; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D000072236:Methyl-Accepting Chemotaxis Proteins; D020409:Molecular Motor Proteins / Q000502:physiology*; D009068:Movement / Q000502:physiology; D011485:Protein Binding; D012399:Rotation; D013696:Temperature; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D020409:Molecular Motor Proteins; C000607606:cheY protein, E coli