Contribution of Many Charged Residues at the Stator-Rotor Interface of the Na+-Driven Flagellar Motor to Torque Generation in Vibrio alginolyticus

In torque generation by the bacterial flagellar motor, it has been suggested that electrostatic interactions between charged residues of MotA and FliG at the rotor-stator interface are important. However, the actual role(s) of those charged residues has not yet been clarified. In this study, we syst...

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Bibliographic Details
Published in:Journal of bacteriology 2014-04, Vol.196 (7), p.1377-1385
Main Authors: Takekawa, Norihiro, Kojima, Seiji, Homma, Michio
Format: Article
Language:English
Subjects:
Amino Acid Motifs
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Bacteriology
Charged particles
electrostatic interactions
Flagella - chemistry
Flagella - genetics
Flagella - metabolism
Gram-negative bacteria
mutants
Mutation
Sodium
Sodium - metabolism
Sodium Channels - chemistry
Sodium Channels - genetics
Sodium Channels - metabolism
Torque
Vibrio alginolyticus
Vibrio alginolyticus - chemistry
Vibrio alginolyticus - genetics
Vibrio alginolyticus - metabolism
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Summary:In torque generation by the bacterial flagellar motor, it has been suggested that electrostatic interactions between charged residues of MotA and FliG at the rotor-stator interface are important. However, the actual role(s) of those charged residues has not yet been clarified. In this study, we systematically made mutants of Vibrio alginolyticus whose charged residues of PomA (MotA homologue) and FliG were replaced by uncharged or charge-reversed residues and characterized the motilities of those mutants. We found that the members of a group of charged residues, 7 in PomA and 6 in FliG, collectively participate in torque generation of the Na+-driven flagellar motor in Vibrio. An additional specific interaction between PomA-E97 and FliG-K284 is critical for proper performance of the Vibrio motor. Our results also reveal that more charged residues are involved in the PomA-FliG interactions in the Vibrio Na+-driven motor than in the MotA-FliG interactions in the H+-driven one. This suggests that a larger number of conserved charged residues at the PomA-FliG interface contributes to the robustness of the Vibrio motor against mutations. The interaction surfaces of the stator and rotor of the Na+-driven motor seem to be more complex than those previously proposed in the H+-driven motor.
ISSN:0021-9193
1098-5530
DOI:10.1128/jb.01392-13