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1.
Polymers (Basel) ; 14(5)2022 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-35267801

RESUMO

This review is devoted to the application of bulk synthetic polymers such as polysulfone (PSf), polyethersulfone (PES), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF) for the separation of oil-water emulsions. Due to the high hydrophobicity of the presented polymers and their tendency to be contaminated with water-oil emulsions, methods for the hydrophilization of membranes based on them were analyzed: the mixing of polymers, the introduction of inorganic additives, and surface modification. In addition, membranes based on natural hydrophilic materials (cellulose and its derivatives) are given as a comparison.

2.
Proc Natl Acad Sci U S A ; 119(11): e2112799119, 2022 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-35271394

RESUMO

SignificanceComplex cellular processes such as cell migration require coordinated remodeling of both the actin and the microtubule cytoskeleton. The two networks for instance exert forces on each other via active motor proteins. Here we show that, surprisingly, coupling via passive cross-linkers can also result in force generation. We specifically study the transport of actin filaments by growing microtubule ends. We show by cell-free reconstitution experiments, computer simulations, and theoretical modeling that this transport is driven by the affinity of the cross-linker for the chemically distinct microtubule tip region. Our work predicts that growing microtubules could potentially rapidly relocate newly nucleated actin filaments to the leading edge of the cell and thus boost migration.


Assuntos
Actinas , Microtúbulos , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Citoesqueleto/metabolismo , Microtúbulos/metabolismo , Transporte Proteico
3.
Protein Sci ; 31(1): 269-282, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34767272

RESUMO

Small-angle X-ray scattering (SAXS) is an established technique for structural analysis of biological macromolecules in solution. During the last decade, inline chromatography setups coupling SAXS with size exclusion (SEC-SAXS) or ion exchange (IEC-SAXS) have become popular in the community. These setups allow one to separate individual components in the sample and to record SAXS data from isolated fractions, which is extremely important for subsequent data interpretation, analysis, and structural modeling. However, in case of partially overlapping elution peaks, inline chromatography SAXS may still yield scattering profiles from mixtures of components. The deconvolution of these scattering data into the individual fractions is nontrivial and potentially ambiguous. We describe a cross-platform computer program, EFAMIX, for restoring the scattering and concentration profiles of the components based on the evolving factor analysis (EFA). The efficiency of the program is demonstrated in a number of simulated and experimental SEC-SAXS data sets. Sensitivity and limitations of the method are explored, and its applicability to IEC-SAXS data is discussed. EFAMIX requires minimal user intervention and is available to academic users through the program package ATSAS as from release 3.1.


Assuntos
Processamento Eletrônico de Dados , Espalhamento a Baixo Ângulo , Software , Difração de Raios X , Cromatografia
4.
J Biomol Struct Dyn ; 40(8): 3626-3641, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-33225840

RESUMO

Two recombinant purine nucleoside phosphorylases from thermophilic bacterium Thermus thermophilus HB27 encoded by genes TT_C1070 (TthPNPI) and TT_C0194 (TthPNPII) were purified and characterized. The comparative analysis of their sequences, molecular weight, enzymes specificity and kinetics of the catalyzed reaction were realized. As a result, it was determined that the TthPNPI is specific to guanosine while the TthPNPII to adenosine. According to the results of the size exclusion chromatography and SAXS study both enzymes are hexameric molecules. Based on the sequence alignment with homologous purine nucleoside phosphorylases (PNPs), Asn was identified as a purine base recognizing residue in the active site of TthPNPI and Asp in TthPNPII. The three-dimensional structure of TthPNPII was solved at 2.5 Å resolution by molecular replacement method using crystals grown in microgravity. Position of phosphate in the active site cavity is located. The possible arrangement of adenosine and guanosine in TthPNPII active site cavity is considered using superposition with the structures of homologous trimeric and hexameric PNPs complexed with corresponding substrates. The peculiarities of oligomeric structure of TthPNPII in comparison with homologous PNPs are described. It is shown that two trimeric molecules of TthPNPII in the asymmetric part of the unit cell are connected by three two-fold axis into a hexamer with 32-point symmetry. This type of hexameric structure of PNP is found for the first time. The interface area between the subunits in trimeric molecule and between the trimers in TthPNPII hexamer is described.Communicated by Ramaswamy H. Sarma.


Assuntos
Purina-Núcleosídeo Fosforilase , Thermus thermophilus , Adenosina/química , Cristalografia por Raios X , Guanosina , Purina-Núcleosídeo Fosforilase/química , Purina-Núcleosídeo Fosforilase/genética , Purina-Núcleosídeo Fosforilase/metabolismo , Espalhamento a Baixo Ângulo , Especificidade por Substrato , Difração de Raios X
5.
Empir Econ ; : 1-53, 2021 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-34873364

RESUMO

We propose a novel risk measure that is built on comparing high-frequency time-varying volatility and low-frequency return spillover estimates. This measure permits to identify the markets that are epidemic in their complex interdependence. We conjecture that initially a highly volatile market experiences episodes of risk transmission, but only later absorbs risk and becomes an epidemic market. Moreover, we can detect newly emerging 'contagion' in the system. We examine the behaviour of 30 global equity markets and compare spillover measures, which encapsulate many large and small crises episodes. Instead of relying on ex post crisis information, our model identifies crises periods. An important implication of the proposed approach is that highly interrelated markets, such as China, are less likely to transmit a global economic crisis under the current interdependence setting.

6.
Polymers (Basel) ; 13(24)2021 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-34960906

RESUMO

A new method for purification of 2-methyl-2-oxazoline using citric acid was developed and living cationic ring-opening polymerization of 2-methyl-2-oxazoline was carried out. Polymerization was conducted in acetonitrile using benzyl chloride-boron trifluoride etherate initiating system. According to DSC data, the temperature range of melting of the crystalline phase of the resulting polymer was 95-180 °C. According to small-angle X-ray scattering and wide-angle X-ray diffraction data, the degree of crystallinity of the polymer was 12%. Upon cooling of the polymer melt, the polymer became amorphous. Using thermogravimetric analysis, it was found that the thermal destruction of poly(2-methyl-2-oxazoline) started above 209 °C.

7.
Membranes (Basel) ; 11(11)2021 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-34832062

RESUMO

An approximate model based on friction-coefficient formalism is developed to predict the mixed-gas permeability and selectivity of polymeric membranes. More specifically, the model is a modification of Kedem's approach to flux coupling. The crucial assumption of the developed model is the division of the inverse local permeability of the mixture component into two terms: the inverse local permeability of the corresponding pure gas and the term proportional to the friction between penetrants. Analytical expressions for permeability and selectivity of polymeric membranes in mixed-gas conditions were obtained within the model. The input parameters for the model are ideal selectivity and solubility coefficients for pure gases. Calculations have shown that, depending on the input parameters and the value of the membrane Peclét number (the measure of coupling), there can be both a reduction and an enhancement of selectivity compared to the ideal selectivity. The deviation between real and ideal selectivity increases at higher Peclét numbers; in the limit of large Peclét numbers, the mixed-gas selectivity tends to the value of the ideal solubility selectivity. The model has been validated using literature data on mixed-gas separation of n-butane/methane and propylene/propane through polymeric membranes.

8.
Plants (Basel) ; 10(10)2021 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-34685872

RESUMO

Guar gum, a polysaccharide derived from guar seeds, is widely used in a variety of industrial applications, including oil and gas production. Although guar is mostly propagated in India, interest in guar as a new industrial legume crop is increasing worldwide, demanding the development of effective tools for marker-assisted selection. In this paper, we report a wide-ranging set of 4907 common SNPs and 327 InDels generated from RADseq genotyping data of 166 guar plants of different geographical origin. A custom guar reference genome was assembled and used for variant calling. A consensus set of variants was built using three bioinformatic pipelines for short variant discovery. The developed molecular markers were used for genome-wide association study, resulting in the discovery of six markers linked to the variation of an important agronomic trait-percentage of pods matured to the harvest date under long light day conditions. One of the associated variants was found inside the putative transcript sequence homologous to an ABC transporter in Arabidopsis, which has been shown to play an important role in D-myo-inositol phosphates metabolism. Earlier, we suggested that genes involved in myo-inositol phosphate metabolism have significant impact on the early flowering of guar plants. Hence, we believe that the developed SNP set allows for the identification of confident molecular markers of important agrobiological traits.

9.
Genes (Basel) ; 12(7)2021 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-34206279

RESUMO

Guar (Cyamopsis tetragonoloba (L.) Taub.) is an annual legume crop native to India and Pakistan. Seeds of the plant serve as a source of galactomannan polysaccharide (guar gum) used in the food industry as a stabilizer (E412) and as a gelling agent in oil and gas fracturing fluids. There were several attempts to introduce this crop to countries of more northern latitudes. However, guar is a plant of a short photoperiod, therefore, its introduction, for example, to Russia is complicated by a long day length during the growing season. Breeding of new guar varieties insensitive to photoperiod slowed down due to the lack of information on functional molecular markers, which, in turn, requires information on guar genome. Modern breeding strategies, e.g., genomic predictions, benefit from integration of multi-omics approaches such as transcriptome, proteome and metabolome assays. Here we present an attempt to use transcriptome-metabolome integration to understand the genetic determination of flowering time variation among guar plants that differ in their photoperiod sensitivity. This study was performed on nine early- and six delayed-flowering guar varieties with the goal to find a connection between 63 metabolites and 1,067 differentially expressed transcripts using Shiny GAM approach. For the key biomarker of flowering in guar myo-inositol we also evaluated the KEGG biochemical pathway maps available for Arabidopsis thaliana. We found that the phosphatidylinositol signaling pathway is initiated in guar plants that are ready for flowering through the activation of the phospholipase C (PLC) gene, resulting in an exponential increase in the amount of myo-inositol in its free form observed on GC-MS chromatograms. The signaling pathway is performed by suppression of myo-inositol phosphate kinases (phosphorylation) and alternative overexpression of phosphatases (dephosphorylation). Our study suggests that metabolome and transcriptome information taken together, provide valuable information about biomarkers that can be used as a tool for marker-assisted breeding, metabolomics and functional genomics of this important legume crop.


Assuntos
Cyamopsis/genética , Redes e Vias Metabólicas/genética , Metaboloma/genética , Transcriptoma/genética , Biomarcadores/metabolismo , Flores/genética , Flores/crescimento & desenvolvimento , Galactanos/genética , Galactanos/metabolismo , Perfilação da Expressão Gênica , Humanos , Mananas/genética , Mananas/metabolismo , Fotoperíodo , Desenvolvimento Vegetal/genética , Gomas Vegetais/genética , Gomas Vegetais/metabolismo
10.
Plants (Basel) ; 10(6)2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34203712

RESUMO

The Crimean autochthonous grape varieties are unique by their origin and serve as a valuable source for breeding new cultivars with increased salt and frost resistance, as well as high-quality berries. However, they suffer from fungal pathogens, as the dry and hot summer months contribute to the epiphytotic course of diseases. An increase in the resistance of Crimean grape varieties is currently achieved through interspecific hybridization. In this study, we describe the genetic and agrobiological diversity of three hybrid populations obtained using the Vitis interspecific hybrid 'Magarach 31-77-10' as a female parent and Muscadinia rotundifolia × Vitis vinifera BC5 hybrid plants as male parents. The hybrid nature of the populations was assessed using RADseq high-throughput genotyping. We discovered 12,734 SNPs, which were common to all three hybrid populations. We also proved with the SSR markers that the strong powdery and downy mildew resistance of the paternal genotypes is determined by the dominant Run1/Rpv1 locus inherited from M. rotundifolia. As a result, the disease development score (R, %) for both mildew diseases in the female parent 'Magarach 31-77-10' was three times higher than in male parents 2000-305-143 and 2000-305-163 over two years of phytopathological assessment. The highest values of yield-contributing traits (average bunch weight ~197 g and 1.3 kg as yield per plant) were detected in the population 4-11 (♀M. No. 31-77-10 × 2000-305-163). Despite the epiphytotic development of PM, the spread of oidium to the vegetative organs of hybrids 4-11 did not exceed 20%. Some hybrid genotypes with high productivity and resistance to pathogens were selected for further assessment as promising candidates for new varieties.

11.
ACS Nano ; 2021 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-34255478

RESUMO

Because of their unique atomic structure, 2D materials are able to create an up-to-date paradigm in fundamental science and technology on the way to engineering the band structure and electronic properties of materials on the nanoscale. One of the simplest methods along this path is the superposition of several 2D nanomaterials while simultaneously specifying the twist angle between adjacent layers (θ), which leads to the emergence of Moiré superlattices. The key challenge in 2D nanoelectronics is to obtain a nanomaterial with numerous Moiré superlattices in addition to a high carrier mobility in a stable and easy-to-fabricate material. Here, we demonstrate the possibility of synthesizing twisted multilayer graphene (tMLG) with a number of monolayers NL = 40-250 and predefined narrow ranges of θ = 3-8°, θ = 11-15°, and θ = 26-30°. A 2D nature of the electron transport is observed in the tMLG, and its carrier mobilities are close to those of twisted bilayer graphene (tBLG) (with θ = 30°) between h-BN layers. We demonstrate an undoubtful presence of numerous Moiré superlattices simultaneously throughout the entire tMLG thickness, while the periods of these superlattices are rather close to each other. This offers a challenge of producing a next generation of devices for nanoelectronics, twistronics, and neuromorphic computing for large data applications.

12.
J Environ Manage ; 290: 112655, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-33892235

RESUMO

For the first time, the basics of waste-free technology for capturing heavy metal ions from urban surface runoff from residential areas of the city with the final utilization of the regenerate were developed. The technology eliminates the subsequent contamination of the lithosphere and atmosphere by regeneration products. The expediency of using fibrous chemosorbents (cationic and polyampholyte) for capturing heavy metal ions from urban surface runoff of residential areas of megalopolises has been justified because of possibility of recycling heavy metal ions and regenerating the sorbent. Model solutions of Fe, Cu, Zn, Pb salts, as well as samples of solutions of real surface effluents were studied. Small experimental samples of filters of various designs were designed and manufactured. The filters were tested at a functioning treatment facility. It was demonstrated that the content of Fe3+, Cu2+, Zn2+, and Pb2+ ions in real surface effluents decreased by 1.4-7 times after passing the effluents even through these small experimental filters. The expediency and possibility of recycling the regenerate as inorganic pigments for the paint industry is shown.


Assuntos
Metais Pesados , Poluentes do Solo , China , Cidades , Monitoramento Ambiental , Metais Pesados/análise , Reciclagem , Poluentes do Solo/análise , Tecnologia
13.
Polymers (Basel) ; 13(7)2021 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-33806130

RESUMO

In this study, the nanoscale transformation of the polylactic-co-glycolic acid (PLGA) internal structure, before and after its supercritical carbon dioxide (sc-CO2) swelling and plasticization, followed by foaming after a CO2 pressure drop, was studied by small-angle X-ray scattering (SAXS) for the first time. A comparative analysis of the internal structure data and porosity measurements for PLGA scaffolds, produced by sc-CO2 processing, on a scale ranging from 0.02 to 1000 µm, was performed by SAXS, helium pycnometry (HP), mercury intrusion porosimetry (MIP) and both "lab-source" and synchrotron X-ray microtomography (micro-CT). This approach opens up possibilities for the wide-scale evaluation, computer modeling, and prediction of the physical and mechanical properties of PLGA scaffolds, as well as their biodegradation behavior in the body. Hence, this study targets optimizing the process parameters of PLGA scaffold fabrication for specific biomedical applications.

14.
Int J Biol Macromol ; 169: 583-596, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33385454

RESUMO

Protealysin is a Serratia proteamaculans metalloproteinase of the M4 peptidase family and the prototype of a large group of protealysin-like proteases (PLPs). PLPs are likely involved in bacterial interaction with plants and animals as well as in bacterial pathogenesis. We demonstrated that the PLP genes in bacteria colocalize with the genes of putative conserved proteins. In S. proteamaculans, these two genes form a bicistronic operon. The putative S. proteamaculans protein that we called emfourin (M4in) was expressed in Escherichia coli and characterized. M4in forms a complex with protealysin with a 1:1 stoichiometry and is a potent slow-binding competitive inhibitor of protealysin (Ki = 52 ± 14 pM); besides, M4in is not secreted from S. proteamaculans constitutively. A comparison of amino acid sequences of M4in and its homologs with those of known inhibitors suggests that M4in is the prototype of a new family of protein inhibitors of proteases.


Assuntos
Metaloproteases/antagonistas & inibidores , Metaloproteases/genética , Serratia/enzimologia , Serratia/genética , Sequência de Aminoácidos , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/farmacologia , Inibidores Enzimáticos/farmacologia , Escherichia coli/genética , Metaloproteases/química , Metaloproteases/metabolismo , Óperon/genética , Peptídeo Hidrolases/metabolismo , Serratia/metabolismo
15.
Membranes (Basel) ; 10(12)2020 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-33327393

RESUMO

The mitigation of the physical aging of thin-film composite (TFC) poly[1-trimethylsilyl-1-propyne] (PTMSP) membranes was studied via the simultaneous application of a polymer-selective layer crosslinking and mixed-matrix membrane approach. For the first time, a recently developed highly porous activated carbon material (infrared (IR) pyrolyzed poly[acrylonitrile] (PAN) or IR-PAN-a) was investigated as an additive to a PTMSP-selective layer for the reduction of aging in TFC membranes. The total electric energy spent on the IR irradiation treatment of IR-PAN-a particles was twice lower than conventional heating. The flat-sheet porous microfiltration membrane MFFK-1 was used as a support, and the crosslinked PTMSP/PEI loaded with a porous filler was applied as a selective layer (0.8-1.8 µm thick) to the TFC membranes. The initial IR-PAN-a sample was additionally milled to obtain a milled IR-PAN-aM sample with a monomodal particle size distribution of 500-800 nm. It was shown that IR-PAN-a, as a filler material with a high surface area and pore volume (2450 m2/g and 1.06 cm3/g, respectively) and a well-developed sponge-like structure, leads to the increase of the N2, O2, and CO2 permeance of PTMSP-based hybrid membrane material and the decrease of the aging of PTMSP. The simultaneous effect of crosslinking and the addition of a highly porous filler essentially improved the aging behavior of PTMSP-based TFC membranes. The monomodal and narrow particle size distribution of highly porous activated IR-pyrolyzed PAN is a key factor for the production of TFC membranes with reduced aging. The highest stability was achieved by the addition of a milled IR-PAN-aM sample (10 wt%). TFC membrane permeance was 6300 GPU (30% of initial permeance) after 11,000 h of aging at ambient laboratory conditions.

16.
Essays Biochem ; 64(2): 371-382, 2020 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-32502246

RESUMO

Microtubules are dynamic polymers that grow and shrink through addition or loss of tubulin subunits at their ends. Microtubule ends generate mechanical force that moves chromosomes and cellular organelles, and provides mechanical tension. Recent literature describes a number of proteins and protein complexes that couple dynamics of microtubule ends to movements of their cellular cargoes. These 'couplers' are quite diverse in their microtubule-binding domains (MTBDs), while sharing similarity in function, but a systematic understanding of the principles underlying their activity is missing. Here, I review various types of microtubule couplers, focusing on their essential activities: ability to follow microtubule ends and capture microtubule-generated force. Most of the couplers require presence of unstructured positively charged sequences and multivalency in their microtubule-binding sites to efficiently convert the microtubule-generated force into useful connection to a cargo. An overview of the microtubule features supporting end-tracking and force-coupling, and the experimental methods to assess force-coupling properties is also provided.


Assuntos
Proteínas dos Microtúbulos , Microtúbulos , Moduladores de Tubulina/metabolismo , Humanos , Cinetocoros/metabolismo , Proteínas dos Microtúbulos/química , Proteínas dos Microtúbulos/metabolismo , Microtúbulos/química , Microtúbulos/metabolismo , Saccharomyces cerevisiae
17.
Polymers (Basel) ; 12(6)2020 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-32466559

RESUMO

For the first time, the effect of the side-chain in polyalkylmethylsiloxane towards pervaporative removal of methyl tert-butyl ether (MTBE) from water was studied. The noticeable enhancement of separation factor during the pervaporation of 1 wt.% MTBE solution in water through the dense film (40-50 µm) can be achieved by substitution of a methyl group (separation factor 111) for heptyl (161), octyl (169) or decyl (180) one in polyalkylmethylsiloxane. Composite membrane with the selective layer (~8 µm) made of polydecylmethylsiloxane (M10) on top of microfiltration support (MFFK membrane) demonstrated MTBE/water separation factor of 310, which was 72% greater than for the dense film (180). A high separation factor together with an overall flux of 0.82 kg·m-2·h-1 allowed this M10/MFFK composite membrane to outperform the commercial composite membranes. The analysis of the concentration polarization modulus and the boundary layer thickness revealed that the feed flow velocity should be gradually increased from 5 cm·s-1 for an initial solution (1 wt.% of MTBE in water) to 13 cm·s-1 for a depleted solution (0.2 wt.% of MTBE in water) to overcome the concentration polarization phenomena in case of composite membrane M10/MFFK (Texp = 50 °C).

18.
Acta Crystallogr A Found Adv ; 76(Pt 2): 163-171, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-32124854

RESUMO

The theoretical framework and a joint quasi-Newton-Levenberg-Marquardt-simulated annealing (qNLMSA) algorithm are established to treat an inverse X-ray diffraction tomography (XRDT) problem for recovering the 3D displacement field function fCtpd(r - r0) = h · u(r - r0) due to a Coulomb-type point defect (Ctpd) located at a point r0 within a crystal [h is the diffraction vector and u(r - r0) is the displacement vector]. The joint qNLMSA algorithm operates in a special sequence to optimize the XRDT target function {\cal F}\{ {\cal P} \} in a χ2 sense in order to recover the function fCtpd(r - r0) [{\cal P} is the parameter vector that characterizes the 3D function fCtpd(r - r0) in the algorithm search]. A theoretical framework based on the analytical solution of the Takagi-Taupin equations in the semi-kinematical approach is elaborated. In the case of true 2D imaging patterns (2D-IPs) with low counting statistics (noise-free), the joint qNLMSA algorithm enforces the target function {\cal F} \{ {\cal P} \} to tend towards the global minimum even if the vector {\cal P} in the search is initially chosen rather a long way from the true one.

19.
Curr Biol ; 30(6): 972-987.e12, 2020 03 23.
Artigo em Inglês | MEDLINE | ID: mdl-32032506

RESUMO

Microtubule-dependent organization of membranous organelles occurs through motor-based pulling and by coupling microtubule dynamics to membrane remodeling. For example, tubules of endoplasmic reticulum (ER) can be extended by kinesin- and dynein-mediated transport and through the association with the tips of dynamic microtubules. The binding between ER and growing microtubule plus ends requires End Binding (EB) proteins and the transmembrane protein STIM1, which form a tip-attachment complex (TAC), but it is unknown whether these proteins are sufficient for membrane remodeling. Furthermore, EBs and their partners undergo rapid turnover at microtubule ends, and it is unclear how highly transient protein-protein interactions can induce load-bearing processive motion. Here, we reconstituted membrane tubulation in a minimal system with giant unilamellar vesicles, dynamic microtubules, an EB protein, and a membrane-bound protein that can interact with EBs and microtubules. We showed that these components are sufficient to drive membrane remodeling by three mechanisms: membrane tubulation induced by growing microtubule ends, motor-independent membrane sliding along microtubule shafts, and membrane pulling by shrinking microtubules. Experiments and modeling demonstrated that the first two mechanisms can be explained by adhesion-driven biased membrane spreading on microtubules. Optical trapping revealed that growing and shrinking microtubule ends can exert forces of ∼0.5 and ∼5 pN, respectively, through attached proteins. Rapidly exchanging molecules that connect membranes to dynamic microtubules can thus bear a sufficient load to induce membrane deformation and motility. Furthermore, combining TAC components and a membrane-attached kinesin in the same in vitro assays demonstrated that they can cooperate in promoting membrane tubule extension.


Assuntos
Retículo Endoplasmático/fisiologia , Proteínas de Escherichia coli/metabolismo , Escherichia coli/fisiologia , Proteínas de Membrana/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/fisiologia , /metabolismo , Microtúbulos/metabolismo
20.
Elife ; 82019 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-31804178

RESUMO

Errorless chromosome segregation requires load-bearing attachments of the plus ends of spindle microtubules to chromosome structures named kinetochores. How these end-on kinetochore attachments are established following initial lateral contacts with the microtubule lattice is poorly understood. Two microtubule-binding complexes, the Ndc80 and Ska complexes, are important for efficient end-on coupling and may function as a unit in this process, but precise conditions for their interaction are unknown. Here, we report that the Ska-Ndc80 interaction is phosphorylation-dependent and does not require microtubules, applied force, or several previously identified functional determinants including the Ndc80-loop and the Ndc80-tail. Both the Ndc80-tail, which we reveal to be essential for microtubule end-tracking, and Ndc80-bound Ska stabilize microtubule ends in a stalled conformation. Modulation of force-coupling efficiency demonstrates that the duration of stalled microtubule disassembly predicts whether a microtubule is stabilized and rescued by the kinetochore, likely reflecting a structural transition of the microtubule end.


Assuntos
Proteínas do Citoesqueleto/química , Proteínas do Citoesqueleto/metabolismo , Microtúbulos/química , Microtúbulos/metabolismo , Aurora Quinase B/genética , Aurora Quinase B/metabolismo , Proteína Quinase CDC2/genética , Proteína Quinase CDC2/metabolismo , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona , Segregação de Cromossomos , Proteínas do Citoesqueleto/genética , Humanos , Cinetocoros/metabolismo , Proteínas Associadas aos Microtúbulos/química , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Modelos Moleculares , Fosforilação , Ligação Proteica , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Análise de Sequência de Proteína , Fuso Acromático/metabolismo
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