title: Adjusting the spokes of the flagellar motor with the DNA-binding protein H-NS.
abstract: The H-NS protein of bacteria is a global regulator that stimulates transcription of flagellar genes and that also acts directly to modulate flagellar motor function. H-NS is known to bind FliG, a protein of the rotor that interacts with the stator and is directly involved in rotation of the motor. Here, we find that H-NS, well known for its ability to organize DNA, acts in the flagellar motor to organize protein subunits in the rotor. It binds to a middle domain of FliG that bridges the core parts of the rotor and parts nearer the edge that interact with the stator. In the absence of H-NS the organization of FliG subunits is disrupted, whereas overexpression of H-NS enhances FliG organization as monitored by targeted disulfide cross-linking, alters the disposition of a helix joining the middle and C-terminal domains of FliG, and enhances motor performance under conditions requiring a strengthened rotor-stator interface. The H-NS homolog StpA was also shown to bind FliG and to act similarly, though less effectively, in organizing FliG. The motility-enhancing effects of H-NS contrast with those of the recently characterized motility inhibitor YcgR. The present findings provide an integrated, structurally grounded framework for understanding the roughly opposing effects of these motility regulators.
authors: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
authors: Koushik
authors: K
authors: Paul
authors: William C
authors: WC
authors: Carlquist
authors: David F
authors: DF
authors: Blair
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015870:Gene Expression; D055786:Gene Knockout Techniques; D008124:Locomotion; D046911:Macromolecular Substances / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D046911:Macromolecular Substances; D020409:Molecular Motor Proteins