title: A chimeric N-terminal Escherichia coli--C-terminal Rhodobacter sphaeroides FliG rotor protein supports bidirectional E. coli flagellar rotation and chemotaxis.
abstract: Flagellate bacteria such as Escherichia coli and Salmonella enterica serovar Typhimurium typically express 5 to 12 flagellar filaments over their cell surface that rotate in clockwise (CW) and counterclockwise directions. These bacteria modulate their swimming direction towards favorable environments by biasing the direction of flagellar rotation in response to various stimuli. In contrast, Rhodobacter sphaeroides expresses a single subpolar flagellum that rotates only CW and responds tactically by a series of biased stops and starts. Rotor protein FliG transiently links the MotAB stators to the rotor, to power rotation and also has an essential function in flagellar export. In this study, we sought to determine whether the FliG protein confers directionality on flagellar motors by testing the functional properties of R. sphaeroides FliG and a chimeric FliG protein, EcRsFliG (N-terminal and central domains of E. coli FliG fused to an R. sphaeroides FliG C terminus), in an E. coli FliG null background. The EcRsFliG chimera supported flagellar synthesis and bidirectional rotation; bacteria swam and tumbled in a manner qualitatively similar to that of the wild type and showed chemotaxis to amino acids. Thus, the FliG C terminus alone does not confer the unidirectional stop-start character of the R. sphaeroides flagellar motor, and its conformation continues to support tactic, switch-protein interactions in a bidirectional motor, despite its evolutionary history in a bacterium with a unidirectional motor.
authors.affiliation: Institute of Genetics, School of Biology, University of Nottingham, Medical School, QMC, Nottingham NG7 2UH, United Kingdom.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Morehouse
authors.forename: Ian G
authors.initials: IG
authors.lastname: Goodfellow
authors.forename: R Elizabeth
authors.initials: RE
authors.lastname: Sockett
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D005407:Flagella / Q000737:chemistry / Q000502:physiology*; D015870:Gene Expression; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000502:physiology*; D012399:Rotation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; C075660:Flig protein, Bacteria; D011993:Recombinant Fusion Proteins
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