title: Adaptive remodelling by FliN in the bacterial rotary motor.
abstract: Sensory adaptation in the Escherichia coli chemosensory pathway has been the subject of interest for decades, with investigation focusing on the receptors that process extracellular inputs. Recent studies demonstrate that the flagellar motors responsible for cell locomotion also play a role, adding or subtracting FliM subunits to maximise sensitivity to pathway signals. It is difficult to reconcile this FliM remodelling with the observation that partner FliN subunits are relatively static fixtures in the motor. By fusing a fluorescent protein internally to FliN, we show that there is in fact significant FliN remodelling. The kinetics and stoichiometry of FliN in steady state and in adapting motors are investigated and found to match the behaviour of FliM in all respects except for timescale where FliN rates are about 4 times slower. We notice that motor adaptation is slower in the presence of the fluorescent protein, indicating a possible source for the difference. The behaviour of FliM and FliN is consistent with a kinetic and stoichiometric model that contradicts the traditional view of a packed, rigid motor architecture.
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Branch
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Michael N
authors.initials: MN
authors.lastname: Sayegh
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Chong
authors.initials: C
authors.lastname: Shen
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Vedavalli S J
authors.initials: VSJ
authors.lastname: Nathan
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA. Electronic address: hberg@mcb.harvard.edu.
authors.forename: Howard C
authors.initials: HC
authors.lastname: Berg
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D005407:Flagella / Q000378:metabolism*; D020409:Molecular Motor Proteins / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C077389:FliN protein, Bacteria; D020409:Molecular Motor Proteins; C066821:FliM protein, Bacteria
keywords: Escherichia coli; bacterial motility; protein subunit exchange; sensory adaptation; signal transduction