scholarly journals Impact of fluorescent protein fusions on the bacterial flagellar motor

2017 ◽  
Author(s):  
M Heo ◽  
AL Nord ◽  
D Chamousset ◽  
E van Rijn ◽  
HJE Beaumont ◽  
...  
Keyword(s):  
Side Effects ◽  
Protein Function ◽  
Fusion Proteins ◽  
Fluorescent Proteins ◽  
Protein Complexes ◽  
Switching Frequency ◽  
Flagellar Motor ◽  
Internal Dynamics ◽  
Biologically Relevant ◽  
Bacterial Flagellar Motor

AbstractFluorescent fusion proteins open a direct and unique window onto protein function. However, they also introduce the risk of perturbation of the function of the native protein. Successful applications of fluorescent fusions therefore rely on a careful assessment and minimization of the side effects. Such insight, however, is still lacking for many applications of fluorescent fusions. This is particularly relevant in the study of the internal dynamics of motor protein complexes, where both the chemical and mechanical reaction coordinates can be affected. Fluorescent proteins fused to thestatorof the bacterial flagellar motor (BFM) complex have previously been used to successfully unveil the internal subunit dynamics of the motor. Here we report the effects of three different fluorescent proteins fused to the stator, all of which altered BFM behavior. The torque generated by individual stators was reduced while their stoichiometry in the complex remained unaffected. MotB fusions decreased the rotation-direction switching frequency of single motors and induced a novel BFM behavior: a bias-dependent asymmetry in the speed attained in the two rotation directions. All these effects could be mitigated by the insertion of a linker at the fusion point. These findings provide a quantitative account of the effects of fluorescent fusions on BFM dynamics and their alleviation—new insights that advance the use of fluorescent fusions to probe the dynamics of protein complexes.Author summaryMuch of what is known about the biology of proteins was discovered by fusing them to fluorescent proteins that allow detection of their location. But the label comes at a cost: the presence of the tag can alter the behavior of the protein of interest in unforeseen, yet biologically relevant ways. These side effects limit the depth to which fluorescent proteins can be used to probe protein function. One of the systems that has been successfully studied with fluorescent fusions for which these effects have not been addressed are dynamic protein complexes that carry out mechanical work. We examined how fluorescent proteins fused to a component of the bacterial flagellar motor complex impacts its function. Our findings show that the fusion proteins altered biologically relevant dynamical properties of the motor, including induction of a novel mechanical behavior, and demonstrate an approach to alleviate this. These results advance our ability to dissect the bacterial flagellar motor, and the internal dynamics of protein complexes in general, with fluorescent fusion proteins while causing minimal perturbation.

Assembly and Dynamics of the Bacterial Flagellum

2020 ◽  
Vol 74 (1) ◽  
pp. 181-200 ◽  
Author(s):  
Judith P. Armitage ◽  
Richard M. Berry
Keyword(s):  
Single Molecule ◽  
Protein Complexes ◽  
Complex Structure ◽  
Live Cells ◽  
Flagellar Motor ◽  
Interacting Protein ◽  
Bacterial Flagellum ◽  
Bacterial Flagellar Motor ◽  
The Stability

The bacterial flagellar motor is the most complex structure in the bacterial cell, driving the ion-driven rotation of the helical flagellum. The ordered expression of the regulon and the assembly of the series of interacting protein rings, spanning the inner and outer membranes to form the ∼45–50-nm protein complex, have made investigation of the structure and mechanism a major challenge since its recognition as a rotating nanomachine about 40 years ago. Painstaking molecular genetics, biochemistry, and electron microscopy revealed a tiny electric motor spinning in the bacterial membrane. Over the last decade, new single-molecule and in vivo biophysical methods have allowed investigation of the stability of this and other large protein complexes, working in their natural environment inside live cells. This has revealed that in the bacterial flagellar motor, protein molecules in both the rotor and stator exchange with freely circulating pools of spares on a timescale of minutes, even while motors are continuously rotating. This constant exchange has allowed the evolution of modified components allowing bacteria to keep swimming as the viscosity or the ion composition of the outside environment changes.

scholarly journals Positive Functional Synergy of Structurally Integrated, Designed Artificial Protein Dimers Assembled by Fully Genetically Encoded Click Chemistry

2018 ◽  
Author(s):  
Harley L. Worthy ◽  
Husam Sabah Auhim ◽  
William David Jamieson ◽  
Jacob pope ◽  
Aaron Wall ◽  
...  
Keyword(s):  
Long Range ◽  
Single Molecule ◽  
Protein Function ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Protein Complexes ◽  
Positive Functional ◽  
Protein Dimers ◽  
Single Molecule Analysis ◽  
Artificial Protein

We combined <i>in silico</i>modelling with fully genetically encoded strain promoted azide-alkyne cycloaddition, to construct bespoke protein dimers. Using fluorescent proteins GFP and Venus as models, homo and heterodimers were constructed that switched ON once assembled and displayed enhanced spectral properties. The determined molecular structure reveals long range polar bond networks involving amino acids and structured water molecules play a key role in activation and functional enhancement by directly linking the two functional centres. Single molecule analysis revealed the dimer is more resistant to photobleaching spending longer times in the ON state with only one CRO likely to be active at any one time. Thus, genetically encoded bioorthogonal chemistry can be used beyond simple passive linkage approaches to generate new and truly integrated protein complexes that form long range bonds networks, which have a profound effect on function and our understanding of fluorescent protein function.

scholarly journals Mechanosensitive remodeling of the bacterial flagellar motor is independent of direction of rotation

2021 ◽  
Author(s):  
Navish Wadhwa ◽  
Yuhai Tu ◽  
Howard C. Berg
Keyword(s):  
Self Assembly ◽  
External Load ◽  
Protein Complexes ◽  
General Strategy ◽  
Flagellar Motor ◽  
Functional Regulation ◽  
Bacterial Flagellar Motor ◽  
Living Organisms ◽  
Broad Interest ◽  
Insight Into

Motility is critical for the survival and dispersal of bacteria, and it plays an important role during infection. How bacteria regulate motility is thus a question of broad interest. Regulation of bacterial motility by chemical stimuli is well studied, but recent work has added a new dimension to the problem of motility control. The bidirectional flagellar motor of the bacterium Escherichia coli recruits or releases torque-generating units (stator units) in response to changes in load. Here, we show that this mechanosensitive remodeling of the flagellar motor is independent of direction of rotation. Remodeling rate constants in clockwise rotating motors and in counterclockwise rotating motors, measured previously, fall on the same curve if plotted against torque. Increased torque decreases the off rate of stator units from the motor, thereby increasing the number of active stator units at steady state. A simple mathematical model based on observed dynamics provides quantitative insight into the underlying molecular interactions. The torque-dependent remodeling mechanism represents a robust strategy to quickly regulate output (torque) in response to changes in demand (load).SignificanceMacromolecular machines carry out most of the biological functions in living organisms. Despite their significance, we do not yet understand the rules that govern the self-assembly of large multi-protein complexes. The bacterial flagellar motor tunes the assembly of its torque-generating stator complex with changes in external load. Here, we report that clockwise and counterclockwise rotating motors have identical remodeling response to changes in the external load, suggesting a purely mechanical mechanism for this regulation. Autonomous control of self-assembly may be a general strategy for tuning the functional output of protein complexes. The flagellar motor is a prime example of a macromolecular machine in which the functional regulation of assembly can be rigorously studied.

scholarly journals Regulation of Switching Frequency and Bias of the Bacterial Flagellar Motor by CheY and Fumarate

1998 ◽  
Vol 180 (13) ◽  
pp. 3375-3380 ◽  
Author(s):  
Marco Montrone ◽  
Michael Eisenbach ◽  
Dieter Oesterhelt ◽  
Wolfgang Marwan
Keyword(s):  
Response Curve ◽  
Conformational Transition ◽  
Switching Frequency ◽  
Flagellar Motor ◽  
Wild Type ◽  
Clockwise Rotation ◽  
Transient Change ◽  
Computer Aided ◽  
Bacterial Flagellar Motor

ABSTRACT The effect of CheY and fumarate on switching frequency and rotational bias of the bacterial flagellar motor was analyzed by computer-aided tracking of tethered Escherichia coli. Plots of cells overexpressing CheY in a gutted background showed a bell-shaped correlation curve of switching frequency and bias centering at about 50% clockwise rotation. Gutted cells (i.e., withcheA to cheZ deleted) with a low CheY level but a high cytoplasmic fumarate concentration displayed the same correlation of switching frequency and bias as cells overexpressing CheY at the wild-type fumarate level. Hence, a high fumarate level can phenotypically mimic CheY overexpression by simultaneously changing the switching frequency and the bias. A linear correlation of cytoplasmic fumarate concentration and clockwise rotation bias was found and predicts exclusively counterclockwise rotation without switching when fumarate is absent. This suggests that (i) fumarate is essential for clockwise rotation in vivo and (ii) any metabolically induced fluctuation of its cytoplasmic concentration will result in a transient change in bias and switching probability. A high fumarate level resulted in a dose-response curve linking bias and cytoplasmic CheY concentration that was offset but with a slope similar to that for a low fumarate level. It is concluded that fumarate and CheY act additively presumably at different reaction steps in the conformational transition of the switch complex from counterclockwise to clockwise motor rotation.

scholarly journals Torque-dependent remodeling of the bacterial flagellar motor

2019 ◽  
pp. 201904577 ◽  
Author(s):  
Navish Wadhwa ◽  
Rob Phillips ◽  
Howard C. Berg
Keyword(s):  
Free Energy ◽  
Self Assembly ◽  
Scientific Literature ◽  
Protein Complexes ◽  
Flagellar Motor ◽  
Motor Speed ◽  
Binding Rate ◽  
Motor Load ◽  
Bacterial Flagellar Motor

Multisubunit protein complexes are ubiquitous in biology and perform a plethora of essential functions. Most of the scientific literature treats such assemblies as static: their function is assumed to be independent of their manner of assembly, and their structure is assumed to remain intact until they are degraded. Recent observations of the bacterial flagellar motor, among others, bring these notions into question. The torque-generating stator units of the motor assemble and disassemble in response to changes in load. Here, we used electrorotation to drive tethered cells forward, which decreases motor load, and measured the resulting stator dynamics. No disassembly occurred while the torque remained high, but all of the stator units were released when the motor was spun near the zero-torque speed. When the electrorotation was turned off, so that the load was again high, stator units were recruited, increasing motor speed in a stepwise fashion. A model in which speed affects the binding rate and torque affects the free energy of bound stator units captures the observed torque-dependent stator assembly dynamics, providing a quantitative framework for the environmentally regulated self-assembly of a major macromolecular machine.

scholarly journals Positive Functional Synergy of Structurally Integrated, Designed Artificial Protein Dimers Assembled by Fully Genetically Encoded Click Chemistry

2018 ◽  
Author(s):  
Harley L. Worthy ◽  
Husam Sabah Auhim ◽  
William David Jamieson ◽  
Jacob pope ◽  
Aaron Wall ◽  
...  
Keyword(s):  
Long Range ◽  
Single Molecule ◽  
Protein Function ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Protein Complexes ◽  
Positive Functional ◽  
Protein Dimers ◽  
Single Molecule Analysis ◽  
Artificial Protein

We combined <i>in silico</i>modelling with fully genetically encoded strain promoted azide-alkyne cycloaddition, to construct bespoke protein dimers. Using fluorescent proteins GFP and Venus as models, homo and heterodimers were constructed that switched ON once assembled and displayed enhanced spectral properties. The determined molecular structure reveals long range polar bond networks involving amino acids and structured water molecules play a key role in activation and functional enhancement by directly linking the two functional centres. Single molecule analysis revealed the dimer is more resistant to photobleaching spending longer times in the ON state with only one CRO likely to be active at any one time. Thus, genetically encoded bioorthogonal chemistry can be used beyond simple passive linkage approaches to generate new and truly integrated protein complexes that form long range bonds networks, which have a profound effect on function and our understanding of fluorescent protein function.

Motility Protein Complexes in the Bacterial Flagellar Motor

1996 ◽  
Vol 261 (2) ◽  
pp. 209-221 ◽  
Author(s):  
Hua Tang ◽  
Timothy F. Braun ◽  
David F. Blair
Keyword(s):  
Protein Complexes ◽  
Flagellar Motor ◽  
Bacterial Flagellar Motor

scholarly journals Application of Cryo-Electron Microscopy on Drug Discovery

2021 ◽  
Vol 27 (S1) ◽  
pp. 3250-3250
Author(s):  
Viswanath Vittaladevaram ◽  
Kranthi Kuruti
Keyword(s):  
Electron Microscopy ◽  
Protein Complexes ◽  
Lead Discovery ◽  
Biologically Relevant ◽  
Biological Targets ◽  
3 Dimensional ◽  
Drug Molecules ◽  
Cryo Electron Microscopy ◽  
Therapeutic Molecules ◽  
Novel Drug

AbstractThe key aspect for development of novel drug molecules is to perform structural determination of target molecule associated with its ligand. One such tool that provides insights towards structure of molecule is Cryo-electron microscopy which covers biological targets that are intractable. Examination of proteins can be carried out in native state, as the samples are frozen at -175 degree Celsius i.e. cryogenic temperatures. In addition to this, there were no limits for molecular and functional structures of proteins that can be imagined in 3-dimensional form. This includes ligands which unravel mechanisms that are biologically relevant. This will enable to better understand the mechanisms that are used for development of new therapeutics. Application of Cryo-electron microscopy is not limited to protein complexes and is considered as non-specific. Intervention of Cryo-EM would allow to analyse the structures and also able to dissect the interaction with therapeutic molecules. The study determines the usage of cryo-EM for providing resolutions that are acceptable for lead discovery. It also provides support for lead optimization and also for discovery of vaccines and therapeutics.

scholarly journals Arabidopsis thaliana G3BP Ortholog Rescues Mammalian Stress Granule Phenotype across Kingdoms

2021 ◽  
Vol 22 (12) ◽  
pp. 6287
Author(s):  
Hendrik Reuper ◽  
Benjamin Götte ◽  
Lucy Williams ◽  
Timothy J. C. Tan ◽  
Gerald M. McInerney ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Fusion Proteins ◽  
Biological Function ◽  
Protein Complexes ◽  
Protein Family ◽  
Knock Out ◽  
Marker Proteins ◽  
Interaction Partners ◽  
Functional Analyses ◽  
Rna Protein Complexes

Stress granules (SGs) are dynamic RNA–protein complexes localized in the cytoplasm that rapidly form under stress conditions and disperse when normal conditions are restored. The formation of SGs depends on the Ras-GAP SH3 domain-binding protein (G3BP). Formations, interactions and functions of plant and human SGs are strikingly similar, suggesting a conserved mechanism. However, functional analyses of plant G3BPs are missing. Thus, members of the Arabidopsis thaliana G3BP (AtG3BP) protein family were investigated in a complementation assay in a human G3BP knock-out cell line. It was shown that two out of seven AtG3BPs were able to complement the function of their human homolog. GFP-AtG3BP fusion proteins co-localized with human SG marker proteins Caprin-1 and eIF4G1 and restored SG formation in G3BP double KO cells. Interaction between AtG3BP-1 and -7 and known human G3BP interaction partners such as Caprin-1 and USP10 was also demonstrated by co-immunoprecipitation. In addition, an RG/RGG domain exchange from Arabidopsis G3BP into the human G3BP background showed the ability for complementation. In summary, our results support a conserved mechanism of SG function over the kingdoms, which will help to further elucidate the biological function of the Arabidopsis G3BP protein family.

scholarly journals Yeast-based automated high-throughput screens to identify anti-parasitic lead compounds

Open Biology ◽  
2013 ◽  
Vol 3 (2) ◽  
pp. 120158 ◽  
Author(s):  
Elizabeth Bilsland ◽  
Andrew Sparkes ◽  
Kevin Williams ◽  
Harry J. Moss ◽  
Michaela de Clare ◽  
...  
Keyword(s):  
Side Effects ◽  
Trypanosoma Brucei ◽  
Fluorescent Proteins ◽  
Screening Method ◽  
Lead Compounds ◽  
Dihydrofolate Reductases ◽  
Parasitic Activity ◽  
High Throughput Screens ◽  
Specific Inhibitors

We have developed a robust, fully automated anti-parasitic drug-screening method that selects compounds specifically targeting parasite enzymes and not their host counterparts, thus allowing the early elimination of compounds with potential side effects. Our yeast system permits multiple parasite targets to be assayed in parallel owing to the strains’ expression of different fluorescent proteins. A strain expressing the human target is included in the multiplexed screen to exclude compounds that do not discriminate between host and parasite enzymes. This form of assay has the advantages of using known targets and not requiring the in vitro culture of parasites. We performed automated screens for inhibitors of parasite dihydrofolate reductases, N -myristoyltransferases and phosphoglycerate kinases, finding specific inhibitors of parasite targets. We found that our ‘hits’ have significant structural similarities to compounds with in vitro anti-parasitic activity, validating our screens and suggesting targets for hits identified in parasite-based assays. Finally, we demonstrate a 60 per cent success rate for our hit compounds in killing or severely inhibiting the growth of Trypanosoma brucei , the causative agent of African sleeping sickness.

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