scholarly journals Fluctuations in Intracellular CheY-P Concentration Coordinate Reversals of Flagellar Motors in E. coli

Biomolecules ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1544
Author(s):  
Yong-Suk Che ◽  
Takashi Sagawa ◽  
Yuichi Inoue ◽  
Hiroto Takahashi ◽  
Tatsuki Hamamoto ◽  
...  

Signal transduction utilizing membrane-spanning receptors and cytoplasmic regulator proteins is a fundamental process for all living organisms, but quantitative studies of the behavior of signaling proteins, such as their diffusion within a cell, are limited. In this study, we show that fluctuations in the concentration of the signaling molecule, phosphorylated CheY, constitute the basis of chemotaxis signaling. To analyze the propagation of the CheY-P signal quantitatively, we measured the coordination of directional switching between flagellar motors on the same cell. We analyzed the time lags of the switching of two motors in both CCW-to-CW and CW-to-CCW switching (∆τCCW-CW and ∆τCW-CCW). In wild-type cells, both time lags increased as a function of the relative distance of two motors from the polar receptor array. The apparent diffusion coefficient estimated for ∆τ values was ~9 µm2/s. The distance-dependency of ∆τCW-CCW disappeared upon loss of polar localization of the CheY-P phosphatase, CheZ. The distance-dependency of the response time for an instantaneously applied serine attractant signal also disappeared with the loss of polar localization of CheZ. These results were modeled by calculating the diffusion of CheY and CheY-P in cells in which phosphorylation and dephosphorylation occur in different subcellular regions. We conclude that diffusion of signaling molecules and their production and destruction through spontaneous activity of the receptor array generates fluctuations in CheY-P concentration over timescales of several hundred milliseconds. Signal fluctuation coordinates rotation among flagella and regulates steady-state run-and-tumble swimming of cells to facilitate efficient responses to environmental chemical signals.

1970 ◽  
Vol 50 (1) ◽  
pp. 57-64 ◽  
Author(s):  
P. K. OMANWAR ◽  
J. A. ROBERTSON

A plant growth room experiment was conducted using seven soils of Alberta with a treatment of 300 ppm of P on four of the soils. The contributions to the movement of P to the roots were calculated according to the method of Barber and co-workers, with some modifications. Results of the experiment showed clearly that movement by mass flow was the most important process of P transport to roots in soils treated with 300 ppm of P. Apparent diffusion was found to be the major process of P movement to roots in untreated soils, which included two soils with naturally high levels of available P. Root interception was found to be of least importance in P movement to roots. Since the concentration of P in soil solution affected the amounts of P reaching the roots by diffusion, mass flow or root interception, the importance of the determination of soil solution P is emphasized. A correlation of 0.86 was obtained between the yield and soil solution P concentration of the untreated soils.


NANO ◽  
2009 ◽  
Vol 04 (02) ◽  
pp. 55-67 ◽  
Author(s):  
H. R. KHATAEE ◽  
A. R. KHATAEE

Movement and shape changes are fundamental aspects of all living organisms. This biological motility results from the biological nanomotors, in particular protein nanomotors. Cells contain a variety of protein nanomotors that rotate (e.g., F0F1-ATP synthase or bacterial flagellar motors) or move in a linear fashion (e.g., the kinesin, myosin and dynein motors). F0F1-ATP synthase is one of the ideal nanomotors or energy providing systems for micro/nanomachines because of its small size, smart and perfect structure, and ultra-high energy transfer efficiency. Therefore, in this paper, we have reviewed the structure, mechanism, and potential applications of the F0F1-ATP synthase nanomotor. In all organisms, the F0F1-ATP synthase consists of two distinct nanomotors, F0 and F1. The F0 moiety is embedded in the membrane and is a detergent soluble unit while the F1 moiety protrudes from the membrane and is a water soluble unit. F0F1-ATP synthase operates as two stepper motor/generators coupled by a common shaft and an electrochemical-to-mechanical-to-chemical energy transducer with an astounding 360° rotary motion of subunits. F0F1-ATP synthase nanomotor may enable the creation of a new class of sensors, mechanical force transducers, actuators, and nanomechanical devices. Thus, the F0F1-ATP synthase nanomotor field has expanded into a wide variety of science.


1988 ◽  
Vol 58 (5) ◽  
pp. 247-254 ◽  
Author(s):  
Shui-Lin Chen ◽  
Rolf M. Rohner ◽  
Heinrich Zollinger

The uptake curves of cationic thiazine dyes (based on thionine) and four other cationic dyes were determined for a series of acrylic fibers, consisting of the same polymer but varying porosities. The apparent diffusion coefficients ( Dapp) and the time lag of the dye uptake (Δ t) were calculated. Dapp and Δ t are functions of the size of the dye cations, the porosity of the fiber, and at least one other factor. We detected an influence of the glass transition temperature under dyeing conditions on the time lag, which was not found before for these or any other fibers.


2021 ◽  
Vol 12 ◽  
Author(s):  
Tsai-Shun Lin ◽  
Seiji Kojima ◽  
Hajime Fukuoka ◽  
Akihiko Ishijima ◽  
Michio Homma ◽  
...  

Bacterial flagellar motor (BFM) is a large membrane-spanning molecular rotary machine for swimming motility. Torque is generated by the interaction between the rotor and multiple stator units powered by ion-motive force (IMF). The number of bound stator units is dynamically changed in response to the external load and the IMF. However, the detailed dynamics of stator unit exchange process remains unclear. Here, we directly measured the speed changes of sodium-driven chimeric BFMs under fast perfusion of different sodium concentration conditions using computer-controlled, high-throughput microfluidic devices. We found the sodium-driven chimeric BFMs maintained constant speed over a wide range of sodium concentrations by adjusting stator units in compensation to the sodium-motive force (SMF) changes. The BFM has the maximum number of stator units and is most stable at 5 mM sodium concentration rather than higher sodium concentration. Upon rapid exchange from high to low sodium concentration, the number of functional stator units shows a rapidly excessive reduction and then resurrection that is different from predictions of simple absorption model. This may imply the existence of a metastable hidden state of the stator unit during the sudden loss of sodium ions.


2005 ◽  
Vol 187 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Karen Lipkow ◽  
Steven S. Andrews ◽  
Dennis Bray

ABSTRACT We describe the use of a computational model to study the effects of cellular architecture and macromolecular crowding on signal transduction in Escherichia coli chemotaxis. A newly developed program, Smoldyn, allows the movement and interaction of a large number of individual molecules in a structured environment to be simulated (S. S. Andrews and D. Bray, Phys. Biol., in press). With Smoldyn, we constructed a three-dimensional model of an E. coli cell and examined the diffusion of CheYp from the cluster of receptors to the flagellar motors under control conditions and in response to attractant and repellent stimuli. Our simulations agree well with experimental observations of cell swimming responses and are consistent with the diffusive behavior expected in wild-type and mutant cells. The high resolution available to us in the new program allows us to calculate the loci of individual CheYp molecules in a cell and the distribution of their lifetimes under different cellular conditions. We find that the time delay between stimulus and response differs for flagellar motors located at different positions in the cell. We explore different possible locations for the phosphatase CheZ and show conditions under which a gradient of CheYp exists in the cell. The introduction of inert blocks into the cytoplasm, representing impenetrable structures such as the nucleoid and large protein complexes, produces a fall in the apparent diffusion coefficient of CheYp and enhances the differences between motors. These and other results are left as predictions for future experiments.


1997 ◽  
Vol 161 ◽  
pp. 437-442
Author(s):  
Salvatore Di Bernardo ◽  
Romana Fato ◽  
Giorgio Lenaz

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.


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