scholarly journals Structure and function of stator units of the bacterial flagellar motor

2020 ◽  
Author(s):  
Mònica Santiveri ◽  
Aritz Roa-Eguiara ◽  
Caroline Kühne ◽  
Navish Wadhwa ◽  
Howard C. Berg ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Mechanistic Model ◽  
Structural Data ◽  
Structural Basis ◽  
Flagellar Motor ◽  
Functional Studies ◽  
Torque Generation ◽  
Bacterial Flagellar Motor ◽  
And Function ◽  
Key Residues

AbstractMany bacteria use the flagellum for locomotion and chemotaxis. Its bi-directional rotation is driven by the membrane-embedded motor, which uses energy from the transmembrane ion gradient to generate torque at the interface between stator units and rotor. The structural organization of the stator unit (MotAB), its conformational changes upon ion transport and how these changes power rotation of the flagellum, remain unknown. Here we present ~3 Å-resolution cryo-electron microscopy reconstructions of the stator unit in different functional states. We show that the stator unit consists of a dimer of MotB surrounded by a pentamer of MotA. Combining structural data with mutagenesis and functional studies, we identify key residues involved in torque generation and present a mechanistic model for motor function and switching of rotational direction.One Sentence SummaryStructural basis of torque generation in the bidirectional 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 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 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 Bacterial flagellar motor

2008 ◽  
Vol 41 (2) ◽  
pp. 103-132 ◽  
Author(s):  
Yoshiyuki Sowa ◽  
Richard M. Berry
Keyword(s):  
Single Molecule ◽  
Cell Envelope ◽  
Molecular Motor ◽  
Motive Force ◽  
Flagellar Motor ◽  
Large Size ◽  
Structural Details ◽  
Bacterial Flagellar Motor ◽  
And Function ◽  
Rotary Motor

AbstractThe bacterial flagellar motor is a reversible rotary nano-machine, about 45 nm in diameter, embedded in the bacterial cell envelope. It is powered by the flux of H+or Na+ions across the cytoplasmic membrane driven by an electrochemical gradient, the proton-motive force or the sodium-motive force. Each motor rotates a helical filament at several hundreds of revolutions per second (hertz). In many species, the motor switches direction stochastically, with the switching rates controlled by a network of sensory and signalling proteins. The bacterial flagellar motor was confirmed as a rotary motor in the early 1970s, the first direct observation of the function of a single molecular motor. However, because of the large size and complexity of the motor, much remains to be discovered, in particular, the structural details of the torque-generating mechanism. This review outlines what has been learned about the structure and function of the motor using a combination of genetics, single-molecule and biophysical techniques, with a focus on recent results and single-molecule techniques.

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 Shared requirements for key residues in the antibiotic resistance enzymes ErmC and ErmE suggest a common mode of RNA recognition

2020 ◽  
Vol 295 (51) ◽  
pp. 17476-17485
Author(s):  
Sebastian J. Rowe ◽  
Ryan J. Mecaskey ◽  
Mohamed Nasef ◽  
Rachel C. Talton ◽  
Rory E. Sharkey ◽  
...  
Keyword(s):  
Structural Model ◽  
Structural Data ◽  
Multidrug Resistant ◽  
Saturation Mutagenesis ◽  
23S Rrna ◽  
Binding Assays ◽  
Erythromycin Resistance ◽  
Functional Studies ◽  
Key Residues ◽  
Related Proteins

Erythromycin-resistance methyltransferases are SAM dependent Rossmann fold methyltransferases that convert A2058 of 23S rRNA to m62A2058. This modification sterically blocks binding of several classes of antibiotics to 23S rRNA, resulting in a multidrug-resistant phenotype in bacteria expressing the enzyme. ErmC is an erythromycin resistance methyltransferase found in many Gram-positive pathogens, whereas ErmE is found in the soil bacterium that biosynthesizes erythromycin. Whether ErmC and ErmE, which possess only 24% sequence identity, use similar structural elements for rRNA substrate recognition and positioning is not known. To investigate this question, we used structural data from related proteins to guide site-saturation mutagenesis of key residues and characterized selected variants by antibiotic susceptibility testing, single turnover kinetics, and RNA affinity–binding assays. We demonstrate that residues in α4, α5, and the α5-α6 linker are essential for methyltransferase function, including an aromatic residue on α4 that likely forms stacking interactions with the substrate adenosine and basic residues in α5 and the α5-α6 linker that likely mediate conformational rearrangements in the protein and cognate rRNA upon interaction. The functional studies led us to a new structural model for the ErmC or ErmE-rRNA complex.

scholarly journals Structural Insight into the Binding of TGIF1 to SIN3A PAH2 Domain through a C-Terminal Amphipathic Helix

2021 ◽  
Vol 22 (23) ◽  
pp. 12631
Author(s):  
Xiaoling He ◽  
Yao Nie ◽  
Heng Zhou ◽  
Rui Hu ◽  
Ying Li ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Structural Basis ◽  
Hydrophobic Core ◽  
Amphipathic Helix ◽  
Structural Insight ◽  
Function Relationship ◽  
And Function ◽  
Key Residues ◽  
Hydrophobic Cleft ◽  
Insight Into

TGIF1 is a transcriptional repressor playing crucial roles in human development and function and is associated with holoprosencephaly and various cancers. TGIF1-directed transcriptional repression of specific genes depends on the recruitment of corepressor SIN3A. However, to date, the exact region of TGIF1 binding to SIN3A was not clear, and the structural basis for the binding was unknown. Here, we demonstrate that TGIF1 utilizes a C-terminal domain (termed as SIN3A-interacting domain, SID) to bind with SIN3A PAH2. The TGIF1 SID adopts a disordered structure at the apo state but forms an amphipathic helix binding into the hydrophobic cleft of SIN3A PAH2 through the nonpolar side at the holo state. Residues F379, L382 and V383 of TGIF1 buried in the hydrophobic core of the complex are critical for the binding. Moreover, homodimerization of TGIF1 through the SID and key residues of F379, L382 and V383 was evidenced, which suggests a dual role of TGIF1 SID and a correlation between dimerization and SIN3A-PAH2 binding. This study provides a structural insight into the binding of TGIF1 with SIN3A, improves the knowledge of the structure–function relationship of TGIF1 and its homologs and will help in recognizing an undiscovered SIN3A-PAH2 binder and developing a peptide inhibitor for cancer treatment.

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