scholarly journals Evidence for symmetry in the elementary process of bidirectional torque generation by the bacterial flagellar motor

2010 ◽  
Vol 107 (41) ◽  
pp. 17616-17620 ◽  
Author(s):  
Shuichi Nakamura ◽  
Nobunori Kami-ike ◽  
Jun-ichi P. Yokota ◽  
Tohru Minamino ◽  
Keiichi Namba
Keyword(s):  
Elementary Process ◽  
Flagellar Motor ◽  
Torque Generation ◽  
Bacterial Flagellar Motor

scholarly journals Effect of the MotA(M206I) Mutation on Torque Generation and Stator Assembly in theSalmonellaH+-Driven Flagellar Motor

2019 ◽  
Vol 201 (6) ◽  
Author(s):  
Yuya Suzuki ◽  
Yusuke V. Morimoto ◽  
Kodai Oono ◽  
Fumio Hayashi ◽  
Kenji Oosawa ◽  
...  
Keyword(s):  
Ion Flux ◽  
Motive Force ◽  
Flagellar Motor ◽  
Wild Type ◽  
Torque Generation ◽  
Unit Speed ◽  
Bacterial Flagellar Motor ◽  
Ph Dependent ◽  
Type Motor ◽  
External Ph

ABSTRACTThe bacterial flagellar motor is composed of a rotor and a dozen stators and converts the ion flux through the stator into torque. Each stator unit alternates in its attachment to and detachment from the rotor even during rotation. In some species, stator assembly depends on the input energy, but it remains unclear how an electrochemical potential across the membrane (e.g., proton motive force [PMF]) or ion flux is involved in stator assembly dynamics. Here, we focused on pH dependence of a slow motile MotA(M206I) mutant ofSalmonella. The MotA(M206I) motor produces torque comparable to that of the wild-type motor near stall, but its rotation rate is considerably decreased as the external load is reduced. Rotation assays of flagella labeled with 1-μm beads showed that the rotation rate of the MotA(M206I) motor is increased by lowering the external pH whereas that of the wild-type motor is not. Measurements of the speed produced by a single stator unit using 1-μm beads showed that the unit speed of the MotA(M206I) is about 60% of that of the wild-type and that a decrease in external pH did not affect the MotA(M206I) unit speed. Analysis of the subcellular stator localization revealed that the number of functional stators is restored by lowering the external pH. The pH-dependent improvement of stator assembly was observed even when the PMF was collapsed and proton transfer was inhibited. These results suggest that MotA-Met206 is responsible for not only load-dependent energy coupling between the proton influx and rotation but also pH-dependent stator assembly.IMPORTANCEThe bacterial flagellar motor is a rotary nanomachine driven by the electrochemical transmembrane potential (ion motive force). About 10 stators (MotA/MotB complexes) are docked around a rotor, and the stator recruitment depends on the load, ion motive force, and coupling ion flux. The MotA(M206I) mutation slows motor rotation and decreases the number of docked stators inSalmonella. We show that lowering the external pH improves the assembly of the mutant stators. Neither the collapse of the ion motive force nor a mutation mimicking the proton-binding state inhibited stator localization to the motor. These results suggest that MotA-Met206 is involved in torque generation and proton translocation and that stator assembly is stabilized by protonation of the stator.

scholarly journals Temperature Dependences of Torque Generation and Membrane Voltage in the Bacterial Flagellar Motor

2013 ◽  
Vol 105 (12) ◽  
pp. 2801-2810 ◽  
Author(s):  
Yuichi Inoue ◽  
Matthew A.B. Baker ◽  
Hajime Fukuoka ◽  
Hiroto Takahashi ◽  
Richard M. Berry ◽  
...  
Keyword(s):  
Membrane Voltage ◽  
Flagellar Motor ◽  
Torque Generation ◽  
Temperature Dependences ◽  
Bacterial Flagellar Motor

scholarly journals Mechanics of torque generation in the bacterial flagellar motor

2015 ◽  
Vol 112 (32) ◽  
pp. E4381-E4389 ◽  
Author(s):  
Kranthi K. Mandadapu ◽  
Jasmine A. Nirody ◽  
Richard M. Berry ◽  
George Oster
Keyword(s):  
Conformational Changes ◽  
Specific Model ◽  
Power Stroke ◽  
Flagellar Motor ◽  
Mechanical Explanation ◽  
Proposed Model ◽  
Torque Generation ◽  
Bacterial Flagellar Motor ◽  
Α Helix ◽  
Fundamental Forces

The bacterial flagellar motor (BFM) is responsible for driving bacterial locomotion and chemotaxis, fundamental processes in pathogenesis and biofilm formation. In the BFM, torque is generated at the interface between transmembrane proteins (stators) and a rotor. It is well established that the passage of ions down a transmembrane gradient through the stator complex provides the energy for torque generation. However, the physics involved in this energy conversion remain poorly understood. Here we propose a mechanically specific model for torque generation in the BFM. In particular, we identify roles for two fundamental forces involved in torque generation: electrostatic and steric. We propose that electrostatic forces serve to position the stator, whereas steric forces comprise the actual “power stroke.” Specifically, we propose that ion-induced conformational changes about a proline “hinge” residue in a stator α-helix are directly responsible for generating the power stroke. Our model predictions fit well with recent experiments on a single-stator motor. The proposed model provides a mechanical explanation for several fundamental properties of the flagellar motor, including torque–speed and speed–ion motive force relationships, backstepping, variation in step sizes, and the effects of key mutations in the stator.

scholarly journals Suppressor Analysis of the MotB(D33E) Mutation To Probe Bacterial Flagellar Motor Dynamics Coupled with Proton Translocation

2008 ◽  
Vol 190 (20) ◽  
pp. 6660-6667 ◽  
Author(s):  
Yong-Suk Che ◽  
Shuichi Nakamura ◽  
Seiji Kojima ◽  
Nobunori Kami-ike ◽  
Keiichi Namba ◽  
...  
Keyword(s):  
High Speed ◽  
Proton Translocation ◽  
Energy Coupling ◽  
Flagellar Motor ◽  
Transmembrane Helices ◽  
Wild Type ◽  
Torque Generation ◽  
Serovar Typhimurium ◽  
Bacterial Flagellar Motor ◽  
Protein Instability

ABSTRACT MotA and MotB form the stator of the proton-driven bacterial flagellar motor, which conducts protons and couples proton flow with motor rotation. Asp-33 of Salmonella enterica serovar Typhimurium MotB, which is a putative proton-binding site, is critical for torque generation. However, the mechanism of energy coupling remains unknown. Here, we carried out genetic and motility analysis of a slowly motile motB(D33E) mutant and its pseudorevertants. We first confirmed that the poor motility of the motB(D33E) mutant is due to neither protein instability, mislocalization, nor impaired interaction with MotA. We isolated 17 pseudorevertants and identified the suppressor mutations in the transmembrane helices TM2 and TM3 of MotA and in TM and the periplasmic domain of MotB. The stall torque produced by the motB(D33E) mutant motor was about half of the wild-type level, while those for the pseudorevertants were recovered nearly to the wild-type levels. However, the high-speed rotations of the motors under low-load conditions were still significantly impaired, suggesting that the rate of proton translocation is still severely limited at high speed. These results suggest that the second-site mutations recover a torque generation step involving stator-rotor interactions coupled with protonation/deprotonation of Glu-33 but not maximum proton conductivity.

scholarly journals Structural basis of torque generation in the bi-directional bacterial flagellar motor

2021 ◽  
Author(s):  
Haidai Hu ◽  
Mònica Santiveri ◽  
Navish Wadhwa ◽  
Howard C. Berg ◽  
Marc Erhardt ◽  
...  
Keyword(s):  
Structural Basis ◽  
Flagellar Motor ◽  
Torque Generation ◽  
Bacterial Flagellar Motor

scholarly journals Function of Protonatable Residues in the Flagellar Motor of Escherichia coli: a Critical Role for Asp 32 of MotB

1998 ◽  
Vol 180 (10) ◽  
pp. 2729-2735 ◽  
Author(s):  
Jiadong Zhou ◽  
Leslie L. Sharp ◽  
H. Lucy Tang ◽  
Scott A. Lloyd ◽  
Stephanie Billings ◽  
...  
Keyword(s):  
Additional Data ◽  
Critical Role ◽  
Flagellar Motor ◽  
Ion Flow ◽  
Cytoplasmic Face ◽  
Torque Generation ◽  
Acidic Residues ◽  
Sodium Binding ◽  
Bacterial Flagellar Motor

ABSTRACT Rotation of the bacterial flagellar motor is powered by a transmembrane gradient of protons or, in some species, sodium ions. The molecular mechanism of coupling between ion flow and motor rotation is not understood. The proteins most closely involved in motor rotation are MotA, MotB, and FliG. MotA and MotB are transmembrane proteins that function in transmembrane proton conduction and that are believed to form the stator. FliG is a soluble protein located on the cytoplasmic face of the rotor. Two other proteins, FliM and FliN, are known to bind to FliG and have also been suggested to be involved to some extent in torque generation. Proton (or sodium)-binding sites in the motor are likely to be important to its function and might be formed from the side chains of acidic residues. To investigate the role of acidic residues in the function of the flagellar motor, we mutated each of the conserved acidic residues in the five proteins that have been suggested to be involved in torque generation and measured the effects on motility. None of the conserved acidic residues of MotA, FliG, FliM, or FliN proved essential for torque generation. An acidic residue at position 32 of MotB did prove essential. Of 15 different substitutions studied at this position, only the conservative-replacement D32E mutant retained any function. Previous studies, together with additional data presented here, indicate that the proteins involved in motor rotation do not contain any conserved basic residues that are critical for motor rotation per se. We propose that Asp 32 of MotB functions as a proton-binding site in the bacterial flagellar motor and that no other conserved, protonatable residues function in this capacity.

scholarly journals Torque Generation in the Bacterial Flagellar Motor

2017 ◽  
Vol 112 (3) ◽  
pp. 30a
Author(s):  
Jasmine A. Nirody ◽  
Richard M. Berry ◽  
George Oster
Keyword(s):  
Flagellar Motor ◽  
Torque Generation ◽  
Bacterial Flagellar Motor
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