title: Suppressor mutants from MotB-D24E and MotS-D30E in the flagellar stator complex of Bacillus subtilis.
abstract: The bacterial flagellar motor is mainly energized by either a proton (H(+)) or sodium ion (Na(+)) motive force and the motor torque is generated by interaction at the rotor-stator interface. MotA/MotB-type stators use H(+) as the coupling ion, whereas MotP/MotS- and PomA/PomB-type stators use Na(+). Bacillus subtilis employs both H(+)-coupled MotA/MotB and Na(+)-coupled MotP/MotS stators, which contribute to the torque required for flagellar rotation. In Escherichia coli, there is a universally conserved Asp-32 residue of MotB that is critical for motility and is a predicted H(+)-binding site. In B. subtilis, the conserved aspartic acid residue corresponds to Asp-24 of MotB (MotB-D24) and Asp-30 of MotS (MotS-D30). Here we report the isolation of two mutants, MotB-D24E and MotS-D30E, which showed a non-motile and poorly motile phenotype, respectively. Up-motile mutants were spontaneously isolated from each mutant. We identified a suppressor mutation at MotB-T181A and MotP-L172P, respectively. Mutants MotB-T181A and MotP-L172P showed about 50% motility and a poorly motile phenotype compared to each wild type strain. These suppressor sites were suggested to indirectly affect the structure of the ion influx pathway.
authors.affiliation: Graduate School of Life Sciences, Toyo University.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Kotomi
authors.initials: K
authors.lastname: Koyama
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ito
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics*; D005407:Flagella / Q000235:genetics* / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D011522:Protons; D016415:Sequence Alignment; D012964:Sodium / Q000737:chemistry; D013489:Suppression, Genetic / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D020409:Molecular Motor Proteins; C064779:MotB protein, Bacteria; D011522:Protons; D012964:Sodium