Functional role of a conserved aspartic acid residue in the motor of the Na(+)-driven flagellum from Vibrio cholerae.
The flagellar motor consists of a rotor and a stator and couples the flux of cations (H(+) or Na(+)) to the generation of the torque necessary to drive flagellum rotation. The inner membrane proteins PomA and PomB are stator components of the Na(+)-driven flagellar motor from Vibrio cholerae. Affinity-tagged variants of PomA and PomB were co-expressed in trans in the non-motile V. cholerae pomAB deletion strain to study the role of the conserved D23 in the transmembrane helix of PomB. At pH 9, the D23E variant restored motility to 100% of that observed with wild type PomB, whereas the D23N variant resulted in a non-motile phenotype, indicating that a carboxylic group at position 23 in PomB is important for flagellum rotation. Motility tests at decreasing pH revealed a pronounced decline of flagellar function with a motor complex containing the PomB-D23E variant. It is suggested that the protonation state of the glutamate residue at position 23 determines the performance of the flagellar motor by altering the affinity of Na(+) to PomB. The conserved aspartate residue in the transmembrane helix of PomB and its H(+)-dependent homologs might act as a ligand for the coupling cation in the flagellar motor.
Vorburger
Thomas
T
Biochemisches Institut, Universität Zürich, Zürich, Switzerland.
Stein
Andreas
A
Ziegler
Urs
U
Kaim
Georg
G
Steuber
Julia
J
D001224:Aspartic Acid / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D005407:Flagella / Q000378:metabolism*; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000378:metabolism; D009068:Movement; D050505:Mutant Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014734:Vibrio cholerae / Q000166:cytology / Q000378:metabolism*
D001426:Bacterial Proteins; D020409:Molecular Motor Proteins; D050505:Mutant Proteins; C107540:PomA protein, Vibrio; C107541:PomB protein, Vibrio; D011994:Recombinant Proteins; D015222:Sodium Channels; D001224:Aspartic Acid; D012964:Sodium