scholarly journals Structure and polymerization dynamics of bacterial actin MreB3 and MreB5 involved in Spiroplasma swimming.

2021 ◽  
Author(s):  
Daichi Takahashi ◽  
Ikuko Fujiwara ◽  
Yuya Sasajima ◽  
Akihiro Narita ◽  
Katsumi Imada ◽  
...  
Keyword(s):  
Driving Force ◽  
Cell Shape ◽  
Atp Depletion ◽  
Bacterial Protein ◽  
Amino Acid Motif ◽  
Swimming Motility ◽  
Constant Rate ◽  
Distinct Sequence ◽  
Almost All ◽  
Actin Superfamily

MreB is a bacterial protein belonging to the actin superfamily. It polymerizes into an antiparallel double-stranded filament that generally functions for cell shape determinations by maintaining the cell wall synthesis. Spiroplasma eriocheiris, a helical wall-less bacterium, has five classes of MreB homologs (SpeMreB1-5) that are responsible for its swimming motility. SpeMreB5 is likely responsible for generating the driving force for the swimming motility. However, molecular profiles involved in the swimming motility are poorly understood. Additionally, SpeMreB3 has distinct sequence features from the other SpeMreBs. Here, we have revealed the structures and polymerization dynamics of SpeMreB3 and SpeMreB5. Both SpeMreBs formed antiparallel double-stranded filaments with different characters; SpeMreB3 formed short filaments with slow polymerization, and SpeMreB5 filaments further assembled into bundle structures such as raft and paracrystal. SpeMreB5 filaments hydrolyzed ATP at a constant rate and were depolymerized immediately after ATP depletion. The Pi release rate of SpeMreB3 was much slower than that of SpeMreB5. Our crystal structure of SpeMreB3 and Pi release measurements of SpeMreB3 and SpeMreB5 mutant variants explain that the cause of the slow Pi release is the lack of the amino acid motif "E ... T - X - [DE]", found in almost all MreBs, which probably takes roles to adjust the position and eliminate a proton of the putative nucleophilic water for γ-Pi of AMPPNP. These results show that SpeMreB3 has unique polymerization dynamics without bundle formations, whereas SpeMreB5 shows bundle formations, and its polymerization dynamics occur in the same manner as other actin superfamily members.

scholarly journals Effect of ROCK Pathway Manipulation on Actin Cytoskeleton Architecture: The Third Dimension

2021 ◽  
Author(s):  
Carolin Grandy ◽  
Fabian Port ◽  
Jonas Pfeil ◽  
Kay-Eberhard Gottschalk
Keyword(s):  
Actin Cytoskeleton ◽  
Driving Force ◽  
Cell Shape ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Structural Behaviour ◽  
Actin Organization ◽  
Biochemical Processes ◽  
The Third ◽  
Third Dimension

Abstract The actin cytoskeleton with its dynamic properties serves as the driving force for the movement and division of cells and gives the cell shape and structure. Disorders in the actin cytoskeleton occur in many diseases. Deeper understanding of the regulation is essential in order to better understand these biochemical processes. In our study, we use metal-induced energy transfer (MIET) as a tool to quantitatively examine the rarely considered third dimension of the actin cytoskeleton with nanometer accuracy. In particular, we investigate the influence of different drugs acting on the ROCK pathway on the three-dimensional actin organization. We find that cells treated with inhibitors have a lower actin height to the substrate while treatment with a stimulator for the ROCK pathway increases the actin height to the substrate. This reveals the precise tuning of adhesion and cytoskeleton tension, which leads to a rich three-dimensional structural behaviour of the actin cytoskeleton. This finetuning is differentially affected by either inhibition or stimulation.

scholarly journals Optimization foam mat drying of roselle (Hibiscus sabdariffa L.) extract

2018 ◽  
Vol 159 ◽  
pp. 02073 ◽  
Author(s):  
Mohammad Djaeni ◽  
Febiani Dwi Utari ◽  
Uma Fadzilia Arifin
Keyword(s):  
Driving Force ◽  
Hibiscus Sabdariffa ◽  
Drying Temperature ◽  
Foaming Agents ◽  
Egg Albumin ◽  
Constant Rate ◽  
Optimum Formulation ◽  
Speed Up ◽  
Color Degradation ◽  
Glycerol Mono

In this study, foaming condition of roselle was optimized using response surface methodology (RSM) and the effect of drying characteristic was investigated. Roselle extract was foamed by addition of 1-5% w/w foaming agents (ovalbumin). The foaming stabilizer, glycerol mono stearate (0-1% w/w) was used to remain mechanic and thermodynamic stability of foam. As the response foam density and drainage volume was determined. The optimum foam variable was then dried at various drying temperatures (50-70°C). The moisture content was observed by gravimetry every 10 minutes for 90 minutes. Result showed that optimum formulation was 3.31% egg albumin and 1% GMS. The constant rate of the foam mat drying (temperature 50°C) was 3 times higher than non foam mat drying. Higher drying temperature can speed up the driving force but lead to color degradation.

The distribution of spectrin along the membranes of normal and echinocytic human erythrocytes

1978 ◽  
Vol 34 (1) ◽  
pp. 91-101
Author(s):  
E. Ziparo ◽  
A. Lemay ◽  
V.T. Marchesi
Keyword(s):  
Cell Membrane ◽  
Cell Shape ◽  
Human Erythrocytes ◽  
Atp Depletion ◽  
Red Cell ◽  
Significant Extent ◽  
Red Cell Membrane ◽  
Extrusion Mechanism ◽  
The Stability ◽  
Spectrin Network

Spectrin molecules are distributed uniformly throughout the submembranous regions of intact human erythrocytes. Spectrin does not appear to extend into the red blood cell cytoplasm to any significant extent. Thus, it does not form a recognizable internal scaffolding nor does it seem to connect distant segments of the cell membrane. Spectrin retains its submembranous location in the spiny processes of echinocytes produced by ATP depletion. Thus, these processes do not seem to form by a simple extrusion mechanism powered by contraction of the spectrin network. Spectrin seems to be important for the stability of the lipid bilayer of the red cell membrane, and it probably also plays a role in regulating red cell shape. How it performs either function is still unknown.

scholarly journals Influence of P-Glycoprotein Inhibitors on Accumulation of Macrolides in J774 Murine Macrophages

2003 ◽  
Vol 47 (3) ◽  
pp. 1047-1051 ◽  
Author(s):  
Cristina Seral ◽  
Jean-Michel Michot ◽  
Hugues Chanteux ◽  
Marie-Paule Mingeot-Leclercq ◽  
Paul M. Tulkens ◽  
...  
Keyword(s):  
Cell Surface ◽  
Driving Force ◽  
Atp Depletion ◽  
Proton Gradients ◽  
Murine Macrophages ◽  
Threefold Increase ◽  
P Glycoprotein ◽  
Cell Handling ◽  
Monensin A ◽  
Glycoprotein Inhibitors

ABSTRACT The influence of inhibitors of P-glycoprotein (verapamil [VE], cyclosporine [CY], and GF120918 [GF]) on the cell handling of macrolides (erythromycin [ERY], clarithromycin [CLR], roxithromycin [ROX], azithromycin [AZM], and telithromycin [TEL]) was examined in J774 murine macrophages. The net influx rates of AZM and TEL were increased from 2- to 3.5-fold in the presence of these inhibitors, but their efflux was slowed only marginally. At 3 h, the inhibitors increased the levels of AZM, ERY, and TEL accumulation approximately three- to fourfold (the effect of VE, however, was lower) but did not influence CLR accumulation (the inhibitors had an intermediate behavior on ROX accumulation). The effect was concentration dependent (half-maximal increases in the level of accumulation of AZM were obtained with GF, CY, and VE at 0.5, 5, and 10μ M, respectively). ATP depletion also caused an approximately threefold increase in the level of accumulation of AZM. Two inhibitors of MRP (probenecid [2.5 mM] and gemfibrozil [0.25 mM]) had no effect. Monensin (a proton ionophore) completely suppressed the accumulation of AZM in control cells as well as in cells incubated in the presence of VE, demonstrating that transmembrane proton gradients are the driving force causing the accumulation of AZM in both cases. Yet, VE did not alter the pH of the lysosomes (approximately 5) or of the cytosol (approximately 7.1). P-glycoprotein was detected by immunostaining at the cell surface as well as in intracellular vacuoles (endosomes and lysosomes). The data suggest that the influx of AZM, ERY, TEL, and ROX is adversely influenced by the activity of P-glycoprotein in J774 macrophages, resulting in suboptimal drug accumulation.

Effect of Different Washing Treatments on the Formation of Titanate Nanotubes

2010 ◽  
Vol 663-665 ◽  
pp. 1247-1251 ◽  
Author(s):  
Cheng Yan Liu ◽  
Lei Miao ◽  
Rong Huang ◽  
Sakae Tanemura
Keyword(s):  
Aqueous Solution ◽  
Driving Force ◽  
Deionized Water ◽  
Sodium Ion ◽  
Titanate Nanotubes ◽  
Acidic Solutions ◽  
Ph Values ◽  
Acid Washing ◽  
Almost All ◽  
Titanate Nanosheets

Titanate nanotubes were successfully synthesized by means of an alkaline hydrothermal method and further appropriate post-treatments. The effect of different washing treatments on the formation of titanate nanotubes were systematically studied in this paper. It was found that the washing treatments play an important role in the formation of nanotubes. Treating with 0.1M NaCl aqueous solution mainly resulted in titanate nanosheets while treating with deionized water or 0.1M HCl aqueous solution (1 time, PH>7) can obtain highly crystallized titanate nanotubes. Furthermore, if the PH values of solutions after acid washing processes were below 7, trace of nanotubes can be found but almost all of them were damaged. On the basis of all the present experimental results, we can conclude that titanate nanotubes can be prepared as long as the driving force induced by the imbalance of sodium ion (Na+) concentration on two different sides of nanosheets was appropriate, and meanwhile they were instable in acidic solutions.

Reconstitution of Spiroplasma swimming by expressing two bacterial actins in synthetic minimal bacterium

2021 ◽  
Author(s):  
Hana Kiyama ◽  
Shigeyuki Kakizawa ◽  
Yuya Sasajima ◽  
Yuhei Tahara ◽  
Makoto Miyata
Keyword(s):  
Cell Motility ◽  
Cell Shape ◽  
Swimming Motility ◽  
Common Features ◽  
The Common

Cell motility may originate from the movements of housekeeping proteins after they were amplified and transmitted to cell outside. However, this process is not supported by experimental observations. The swimming motility of Spiroplasma, commensal or parasitic bacteria are caused by the helicity switching of a ribbon-like cytoskeleton, that is composed of six proteins evolved from a nucleosidase and bacterial actin called MreB. Here, we expressed these proteins in a synthetic minimal bacterium, JCVI-syn3B whose genome was computer-designed and chemically synthesized. The synthetic bacterium showed swimming motility with the common features with Spiroplasma swimming. Moreover, combination of two proteins showed helical cell shape and swimming, suggesting that the swimming was originated from differentiation and coupling of MreB proteins

Time-dependent modulation of capacitative Ca2+ entry signals by plasma membrane Ca2+ pump in endothelium

1998 ◽  
Vol 274 (4) ◽  
pp. C1117-C1128 ◽  
Author(s):  
Andrey Klishin ◽  
Marina Sedova ◽  
Lothar A. Blatter
Keyword(s):  
Plasma Membrane ◽  
Driving Force ◽  
Vascular Endothelial Cells ◽  
Time Dependent ◽  
Vascular Endothelial ◽  
Constant Rate ◽  
Intracellular Ca ◽  
Initial Peak ◽  
Plateau Level

In vascular endothelial cells, depletion of intracellular Ca2+ stores elicited capacitative Ca2+ entry (CCE) that resulted in biphasic changes of intracellular Ca2+ concentration ([Ca2+]i) with a rapid initial peak of [Ca2+]ifollowed by a gradual decrease to a sustained plateau level. We investigated the rates of Ca2+entry, removal, and sequestration during activation of CCE and their respective contributions to the biphasic changes of [Ca2+]i. Ca2+ buffering by mitochondria, removal by Na+/Ca2+exchange, and a fixed electrical driving force for Ca2+ (voltage-clamp experiments) had little effect on the CCE signal. The rates of entry of Mn2+ and Ba2+, used as unidirectional substitutes for Ca2+ entry through the CCE pathway, were constant and did not follow the concomitant changes of [Ca2+]i. Pharmacological inhibition of the plasma membrane Ca2+ pump, however, abolished the secondary decay phase of the CCE transient. The disparity between the biphasic changes of [Ca2+]iand the constant rate of Ca2+entry during CCE was the result of a delayed, Ca2+-dependent activation of the pump. These results suggest an important modulatory role of the plasma membrane Ca2+ pump in the net cellular gain of Ca2+ during CCE.

An extracellular driving force of cell-shape changes

BioEssays ◽  
2004 ◽  
Vol 26 (12) ◽  
pp. 1344-1350 ◽  
Author(s):  
Otto Schmidt ◽  
Ulrich Theopold
Keyword(s):  
Driving Force ◽  
Cell Shape ◽  
Cell Shape Changes ◽  
Shape Changes

scholarly journals Hyperactive mariner transposons are created by mutations that disrupt allosterism and increase the rate of transposon end synapsis

2013 ◽  
Vol 42 (4) ◽  
pp. 2637-2645 ◽  
Author(s):  
Danxu Liu ◽  
Ronald Chalmers
Keyword(s):  
Biochemical Analysis ◽  
Point Mutations ◽  
Double Strand Breaks ◽  
Amino Acid Motif ◽  
Transposase Gene ◽  
Strand Breaks ◽  
Dimer Interface ◽  
Almost All ◽  
New Applications ◽  
Increased Activity

Abstract New applications for transposons in vertebrate genetics have spurred efforts to develop hyperactive variants. Typically, a genetic screen is used to identify several hyperactive point mutations, which are then incorporated in a single transposase gene. However, the mechanisms responsible for the increased activity are unknown. Here we show that several point mutations in the mariner transposase increase their activities by disrupting the allostery that normally serves to downregulate transposition by slowing synapsis of the transposon ends. We focused on the conserved WVPHEL amino acid motif, which forms part of the mariner transposase dimer interface. We generated almost all possible single substitutions of the W, V, E and L residues and found that the majority are hyperactive. Biochemical analysis of the mutations revealed that they disrupt signals that pass between opposite sides of the developing transpososome in response to transposon end binding. In addition to their role in allostery, the signals control the initiation of catalysis, thereby preventing non-productive double-strand breaks. Finally, we note that such breaks may explain the puzzling ‘self-inflicted wounds’ at the ends of the Mos1 transposon in Drosophila.

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