title: Biophysical characterization of the C-terminal region of FliG, an essential rotor component of the Na+-driven flagellar motor.
abstract: The bacterial flagellar motor generates a rotational force by the flow of ions through the membrane. The rotational force is generated by the interaction between the cytoplasmic regions of the rotor and the stator. FliG is directly involved in the torque generation of the rotor protein by its interaction. FliG is composed of three domains: the N-terminal, Middle and C-terminal domains, based on its structure. The C-terminal domain of FliG is assumed to be important for the interaction with the stator that generates torque. In this study, using CD spectra, gel filtration chromatography and DSC (differential scanning calorimetry), we characterized the physical properties of the C-terminal domain (G214-Stop) of wild-type (WT) FliG and its non-motile phenotype mutant derivatives (L259Q, L270R and L271P), which were derived from the sodium-driven motor of Vibrio. The CD spectra and gel filtration chromatography revealed a slight difference between the WT and the mutant FliG proteins, but the DSC results suggested a large difference in their stabilities. That structural difference was confirmed by differences in protease sensitivity. Based on these results, we conclude that mutations which confer the non-motile phenotype destabilize the C-terminal domain of FliG.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cyo, Chikusa-ku, Nagoya 464-8602, Japan; and TA Instruments Japan Inc., Gotanda, Shinagawa-ku, Tokyo 141-0031, Japan.
authors.forename: Mizuki
authors.initials: M
authors.lastname: Gohara
authors.forename: Shiori
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Rei
authors.initials: R
authors.lastname: Abe-Yoshizumi
authors.forename: Natsumi
authors.initials: N
authors.lastname: Nonoyama
authors.forename: Seiji
authors.initials: S
authors.lastname: Kojima
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Asami
authors.forename: Michio
authors.initials: M
authors.lastname: Homma
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D015153:Blotting, Western; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D005407:Flagella / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D014733:Vibrio / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C075660:Flig protein, Bacteria
keywords: FliG; differential scanning calorimetry; flagellar motor; rotor