共查询到20条相似文献,搜索用时 248 毫秒
1.
Clara Pereira L. Miguel Martins Lucília Saraiva 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Mutations in LRRK2 are the most common genetic cause of Parkinson's disease (PD). Studies in the yeast Saccharomyces cerevisiae have provided valuable insights into the mechanisms of cellular dysfunction associated with the expression of faulty PD genes.Methods
We developed a yeast model for full-length LRRK2 studies. We expressed wild-type (wt) LRRK2 and mutations and evaluated their role during oxidative stress conditions. The involvement of mitochondria was assessed by using rho-zero mutants and by evaluating reactive oxygen species (ROS) production and mitochondrial membrane potential by flow cytometry. The involvement of endocytosis was also studied by testing several endocytic mutants and by following the vacuolar delivery of the probe FM4-64.Results
Expression of LRRK2 in yeast was associated to increased hydrogen peroxide resistance. This phenotype, which was dependent on mitochondrial function, was not observed for PD-mutants G2019S and R1441C or in the absence of the kinase activity and the WD40 repeat domain. Expression of the pathogenic mutants stimulated ROS production and increased mitochondrial membrane potential. For the PD-mutants, but not for wild-type LRRK2, endocytic defects were also observed. Additionally, several endocytic proteins were required for LRRK2-mediated protection against hydrogen peroxide.Conclusions
Our results indicate that LRRK2 confers cellular protection during oxidative stress depending on mitochondrial function and endocytosis.General significance
Both the loss of capacity of LRRK2 pathogenic mutants to protect against oxidative stress and their enhancement of dysfunction may be important for the development of PD during the aging process. 相似文献2.
Shi-Bei Wu Yu-Ting Wu Tsung-Pu Wu Yau-Huei Wei 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Mitochondrial DNA (mtDNA) mutations are an important cause of mitochondrial diseases, for which there is no effective treatment due to complex pathophysiology. It has been suggested that mitochondrial dysfunction-elicited reactive oxygen species (ROS) plays a vital role in the pathogenesis of mitochondrial diseases, and the expression levels of several clusters of genes are altered in response to the elevated oxidative stress. Recently, we reported that glycolysis in affected cells with mitochondrial dysfunction is upregulated by AMP-activated protein kinase (AMPK), and such an adaptive response of metabolic reprogramming plays an important role in the pathophysiology of mitochondrial diseases.Scope of review
We summarize recent findings regarding the role of AMPK-mediated signaling pathways that are involved in: (1) metabolic reprogramming, (2) alteration of cellular redox status and antioxidant enzyme expression, (3) mitochondrial biogenesis, and (4) autophagy, a master regulator of mitochondrial quality control in skin fibroblasts from patients with mitochondrial diseases.Major conclusion
Induction of adaptive responses via AMPK–PFK2, AMPK–FOXO3a, AMPK–PGC-1α, and AMPK–mTOR signaling pathways, respectively is modulated for the survival of human cells under oxidative stress induced by mitochondrial dysfunction. We suggest that AMPK may be a potential target for the development of therapeutic agents for the treatment of mitochondrial diseases.General significance
Elucidation of the adaptive mechanism involved in AMPK activation cascades would lead us to gain a deeper insight into the crosstalk between mitochondria and the nucleus in affected tissue cells from patients with mitochondrial diseases. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research. 相似文献3.
4.
Anabel Soldano Huili Yao Mario Rivera Eduardo A. Ceccarelli Daniela L. Catalano-Dupuy 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Heme oxygenase catalyzes the conversion of heme to iron, carbon monoxide and biliverdin employing oxygen and reducing equivalents. This enzyme is essential for heme-iron utilization and contributes to virulence in Leptospira interrogans.Methods
A phylogenetic analysis was performed using heme oxygenases sequences from different organisms including saprophytic and pathogenic Leptospira species. L. interrogans heme oxygenase (LepHO) was cloned, overexpressed and purified. The structural and enzymatic properties of LepHO were analyzed by UV–vis spectrophotometry and 1H NMR. Heme-degrading activity, ferrous iron release and biliverdin production were studied with different redox partners.Results
A plastidic type, high efficiently ferredoxin-NADP+ reductase (LepFNR) provides the electrons for heme turnover by heme oxygenase in L. interrogans. This catalytic reaction does not require a ferredoxin. Moreover, LepFNR drives the heme degradation to completeness producing free iron and α-biliverdin as the final products. The phylogenetic divergence between heme oxygenases from saprophytic and pathogenic species supports the functional role of this enzyme in L. interrogans pathogenesis.Conclusions
Heme-iron scavenging by LepHO in L. interrogans requires only LepFNR as redox partner. Thus, we report a new substrate of ferredoxin-NADP+ reductases different to ferredoxin and flavodoxin, the only recognized protein substrates of this flavoenzyme to date. The results presented here uncover a fundamental step of heme degradation in L. interrogans.General significance
Our findings contribute to understand the heme-iron utilization pathway in Leptospira. Since iron is required for pathogen survival and infectivity, heme degradation pathway may be relevant for therapeutic applications. 相似文献5.
Arti Parihar Mordhwaj S. Parihar Rafal Nazarewicz Pedram Ghafourifar 《Biochimica et Biophysica Acta (BBA)/General Subjects》2010
Background
Ceramides are intracellular lipid mediator implicated in various cellular responses, including oxidative stress and programmed cell death. Studies demonstrated strong links between ceramide and the mitochondria in the regulation of apoptosis. However, the mechanism of apoptosis induced by ceramides is not fully understood. The present study delineates importance of the redox state of cytochrome c for release of cytochrome c and apoptosis of human mammary adenocarcinoma MCF-7 and MDA-MB-231 cells induced by ceramides.Methods
The study uses MCF-7 and MDA-MB-231 cells, isolated mitochondria, submitochondrial particles, and oxidized and reduced cytochrome c. Methods used include flow cytometry, immunoblotting, spectroscopy, and respirometry.Results
We show that ceramides induce mitochondrial oxidative stress and release of cytochrome c from the mitochondria of these cells. Our findings show that ceramides react with oxidized cytochrome c whereas reduced cytochrome c does not react with ceramides. We also show that oxidized cytochrome c reacted with ceramides exerts lower reducibility and function to support mitochondrial respiration. Furthermore, our data show that glutathione protects cytochrome c of reacting with ceramides by increasing the reduced state of cytochrome c.Conclusions
Ceramides induce oxidative stress and apoptosis in human mammary adenocarcinoma cells by interacting with oxidized cytochrome c leading to the release of cytochrome c from the mitochondria. Our findings suggest a novel mechanism for protective role of glutathione.General significance
Our study suggests that the redox state of cytochrome c is important in oxidative stress and apoptosis induced by ceramides. 相似文献6.
Claire J. Parker Siburt Timothy A. Mietzner Alvin L. Crumbliss 《Biochimica et Biophysica Acta (BBA)/General Subjects》2012
Background
Gram negative bacteria require iron for growth and virulence. It has been shown that certain pathogenic bacteria such as Neisseria gonorrhoeae possess a periplasmic protein called ferric binding protein (FbpA), which is a node in the transport of iron from the cell exterior to the cytosol.Scope of review
The relevant literature is reviewed which establishes the molecular mechanism of FbpA mediated iron transport across the periplasm to the inner membrane.Major conclusions
Here we establish that FbpA may be considered a bacterial transferrin on structural and functional grounds. Data are presented which suggest a continuum whereby FbpA may be considered as a naked iron carrier, as well as a Fe–chelate carrier, and finally a member of the larger family of periplasmic binding proteins.General significance
An investigation of the molecular mechanisms of action of FbpA as a member of the transferrin super family enhances our understanding of bacterial mechanisms for acquisition of the essential nutrient iron, as well as the modes of action of human transferrin, and may provide approaches to the control of pathogenic diseases. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders. 相似文献7.
Tam Thi Thanh Le Kazuaki Mawatari Miki MaetaniTomomi Yamamoto Sayaka HayashidaHitomi Iba Mutsumi AiharaAkiko Hirata Takaaki ShimohataTakashi Uebanso Akira Takahashi 《Biochimica et Biophysica Acta (BBA)/General Subjects》2012
Background
Reactive oxygen species (ROS), including superoxide anion radical, induce chronic risk of oxidative damage to many cellular macromolecules resulting in damage to cells. Superoxide dismutases (SODs) catalyze the dismutation of superoxide to oxygen and hydrogen peroxide and are a primary defense against ROS. Vibrio parahaemolyticus, a marine bacterium that causes acute gastroenteritis following consumption of raw or undercooked seafood, can survive ROS generated by intestinal inflammatory cells. However, there is little information concerning SODs in V. parahaemolyticus. This study aims to clarify the role of V. parahaemolyticus SODs against ROS.Methods
V. parahaemolyticus SOD gene promoter activities were measured by a GFP reporter assay. Mutants of V. parahaemolyticus SOD genes were constructed and their SOD activity and resistance to oxidative stresses were measured.Results
Bioinformatic analysis showed that V. parahaemolyticus SODs were distinguished by their metal cofactors, FeSOD (VP2118), MnSOD (VP2860), and CuZnSOD (VPA1514). VP2118 gene promoter activity was significantly higher than the other SOD genes. In a VP2118 gene deletion mutant, SOD activity was significantly decreased and could be recovered by VP2118 gene complementation. The absence of VP2118 resulted in significantly lowered resistance to ROS generated by hydrogen peroxide, hypoxanthine–xanthine oxidase, or Paraquat. Furthermore, both the N- and C-terminal SOD domains of VP2118 were necessary for ROS resistance.Conclusion
VP2118 is the primary V. parahaemolyticus SOD and is vital for anti-oxidative stress responses.General significance
The V. parahaemolyticus FeSOD VP2118 may enhance ROS resistance and could promote its survival in the intestinal tract to facilitate host tissue infection. 相似文献8.
Sirena Soriano José V. Llorens Laura Blanco-Sobero Lucía Gutiérrez Pablo Calap-Quintana M. Puerto Morales M. Dolores Moltó M. José Martínez-Sebastián 《Gene》2013
Friedreich's ataxia (FRDA), the most common inherited ataxia, is a neurodegenerative disease caused by a reduction in the levels of the mitochondrial protein frataxin, the function of which remains a controversial matter. Several therapeutic approaches are being developed to increase frataxin expression and reduce the intramitochondrial iron aggregates and oxidative damage found in this disease. In this study, we tested separately the response of a Drosophila RNAi model of FRDA ( Llorens et al., 2007) to treatment with the iron chelator deferiprone (DFP) and the antioxidant idebenone (IDE), which are both in clinical trials. The FRDA flies have a shortened life span and impaired motor coordination, and these phenotypes are more pronounced in oxidative stress conditions. In addition, under hyperoxia, the activity of the mitochondrial enzyme aconitase is strongly reduced in the FRDA flies. This study reports that DFP and IDE improve the life span and motor ability of frataxin-depleted flies. We show that DFP eliminates the excess of labile iron in the mitochondria and thus prevents the toxicity induced by iron accumulation. IDE treatment rescues aconitase activity in hyperoxic conditions. These results validate the use of our Drosophila model of FRDA to screen for therapeutic molecules to treat this disease. 相似文献
9.
Tomomi Izumikawa Kazumasa Saigoh Jun Shimizu Shoji Tsuji Susumu Kusunoki Hiroshi Kitagawa 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Previously, we identified two missense mutations in the chondroitin N-acetylgalactosaminyltransferase-1 gene in patients with neuropathy. These mutations are associated with a profound decrease in chondroitin N-acetylgalactosaminyltransferase-1 enzyme activity. Here, we describe a patient with neuropathy who is heterozygous for a chondroitin synthase-1 mutation. Chondroitin synthase-1 has two glycosyltransferase activities: it acts as a GlcUA and a GalNAc transferase and is responsible for adding repeated disaccharide units to growing chondroitin sulfate chains.Methods
Recombinant wild-type chondroitin synthase-1 enzyme and the F362S mutant were expressed. These enzymes and cells expressing them were then characterized.Results
The mutant chondroitin synthase-1 protein retained approximately 50% of each glycosyltransferase activity relative to the wild-type chondroitin synthase-1 protein. Furthermore, unlike chondroitin polymerase comprised of wild-type chondroitin synthase-1 protein, the non-reducing terminal 4-O-sulfation of GalNAc residues synthesized by chondroitin N-acetylgalactosaminyltransferase-1 did not facilitate the elongation of chondroitin sulfate chains when chondroitin polymerase that consists of the mutant chondroitin synthase-1 protein was used as the enzyme source.Conclusions
The chondroitin synthase-1 F362S mutation in a patient with neuropathy resulted in a decrease in chondroitin polymerization activity and the mutant protein was defective in regulating the number of chondroitin sulfate chains via chondroitin N-acetylgalactosaminyltransferase-1. Thus, the progression of peripheral neuropathies may result from defects in these regulatory systems.General significance
The elongation of chondroitin sulfate chains may be tightly regulated by the cooperative expression of chondroitin synthase-1 and chondroitin N-acetylgalactosaminyltransferase-1 in peripheral neurons and peripheral neuropathies may result from synthesis of abnormally truncated chondroitin sulfate chains. 相似文献10.
Hideaki Tagashira Yasuharu Shinoda Norifumi Shioda Kohji Fukunaga 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Amyotrophic lateral sclerosis (ALS) is a disease caused by motor neuron degeneration. Recently, a novel SIGMAR1 gene variant (p.E102Q) was discovered in some familial ALS patients.Methods
We address mechanisms underlying neurodegeneration caused by the mutation using Neuro2A cells overexpressing σ1RE102Q, a protein of a SIGMAR1 gene variant (p.E102Q) and evaluate potential amelioration by ATP production via methyl pyruvate (MP) treatment.Results
σ1RE102Q overexpression promoted dissociation of the protein from the endoplasmic reticulum (ER) membrane and cytoplasmic aggregation, which in turn impaired mitochondrial ATP production and proteasome activity. Under ER stress conditions, overexpression of wild-type σ1R suppressed ER stress-induced mitochondrial injury, whereas σ1RE102Q overexpression aggravated mitochondrial damage and induced autophagic cell death. Moreover, σ1RE102Q-overexpressing cells showed aberrant extra-nuclear localization of the TAR DNA-binding protein (TDP-43), a condition exacerbated by ER stress. Treatment of cells with the mitochondrial Ca2 + transporter inhibitor Ru360 mimicked the effects of σ1RE102Q overexpression, indicating that aberrant σ1R-mediated mitochondrial Ca2 + transport likely underlies TDP-43 extra-nuclear localization, segregation in inclusion bodies, and ubiquitination. Finally, enhanced ATP production promoted by methyl pyruvate (MP) treatment rescued proteasome impairment and TDP-43 extra-nuclear localization caused by σ1RE102Q overexpression.Conclusions
Our observations suggest that neurodegeneration seen in some forms of ALS are due in part to aberrant mitochondrial ATP production and proteasome activity as well as TDP-43 mislocalization resulting from the SIGMAR1 mutation.General significance
ATP supplementation by MP represents a potential therapeutic strategy to treat ALS caused by SIGMAR1 mutation. 相似文献11.
12.
Carrie A. May John K. Grady Thomas M. Laue Maura Poli Paolo Arosio N. Dennis Chasteen 《Biochimica et Biophysica Acta (BBA)/General Subjects》2010
Background
Ferritin exhibits complex behavior in the ultracentrifuge due to variability in iron core size among molecules. A comprehensive study was undertaken to develop procedures for obtaining more uniform cores and assessing their homogeneity.Methods
Analytical ultracentrifugation was used to measure the mineral core size distributions obtained by adding iron under high- and low-flux conditions to horse spleen (apoHoSF) and human H-chain (apoHuHF) apoferritins.Results
More uniform core sizes are obtained with the homopolymer human H-chain ferritin than with the heteropolymer horse spleen HoSF protein in which subpopulations of HoSF molecules with varying iron content are observed. A binomial probability distribution of H- and L-subunits among protein shells qualitatively accounts for the observed subpopulations. The addition of Fe2+ to apoHuHF produces iron core particle size diameters from 3.8 ± 0.3 to 6.2 ± 0.3 nm. Diameters from 3.4 ± 0.6 to 6.5 ± 0.6 nm are obtained with natural HoSF after sucrose gradient fractionation. The change in the sedimentation coefficient as iron accumulates in ferritin suggests that the protein shell contracts ∼ 10% to a more compact structure, a finding consistent with published electron micrographs. The physicochemical parameters for apoHoSF (15%/85% H/L subunits) are M = 484,120 g/mol, ν? = 0.735 mL/g, s20,w = 17.0 S and D20,w = 3.21 × 10−7 cm2/s; and for apoHuHF M = 506,266 g/mol, ν? = 0.724 mL/g, s20,w = 18.3 S and D20,w = 3.18 × 10−7 cm2/s.Significance
The methods presented here should prove useful in the synthesis of size controlled nanoparticles of other minerals. 相似文献13.
Zhen Yan Shinya FushinobuTakayoshi Wakagi 《Biochimica et Biophysica Acta - Proteins and Proteomics》2014,1844(4):736-743
Heterodimeric 2-oxoacid:ferredoxin oxidoreductase (OFOR) from Sulfolobus tokodaii (StOFOR) has only one [4Fe–4S]2 + cluster, ligated by 4 Cys residues, C12, C15, C46, and C197. The enzyme has no other Cys. To elucidate the role of these Cys residues in holding of the iron–sulfur cluster in the course of oxidative decarboxylation of a 2-oxoacid, one or two of these Cys residues was/were substituted with Ala to yield C12A, C15A, C46A, C197A and C12/15A mutants. All the mutants showed the loss of iron–sulfur cluster, except the C197A one which retained some unidentified type of iron–sulfur cluster. On addition of pyruvate to OFOR, the wild type enzyme exhibited a chromophore at 320 nm and a stable large EPR signal corresponding to a hydroxyethyl-ThDP radical, while the mutant enzymes did not show formation of any radical intermediate or production of acetyl-CoA, suggesting that the intact [4Fe–4S] cluster is necessary for these processes. The stable radical intermediate in wild type OFOR was rapidly decomposed upon addition of CoA in the absence of an electron acceptor. Non-oxidative decarboxylation of pyruvate, yielding acetaldehyde, has been reported to require CoA for other OFORs, but StOFOR catalyzed acetaldehyde production from pyruvate independent of CoA, regardless of whether the iron–sulfur cluster is intact [4Fe–4S] type or not. A comprehensive reaction scheme for StOFOR with a single cluster was proposed. 相似文献
14.
Jure Pohleven Nataša Obermajer Jerica Sabotič Sabina Anžlovar Kristina Sepčić Janko Kos Bogdan Kralj Borut Štrukelj Jože Brzin 《Biochimica et Biophysica Acta (BBA)/General Subjects》2009
Background
Lectins are a diverse group of carbohydrate-binding proteins exhibiting numerous biological activities and functions.Methods
Two-step serial carbohydrate affinity chromatography was used to isolate a lectin from the edible mushroom clouded agaric (Clitocybe nebularis). It was characterized biochemically, its gene and cDNA cloned and the deduced amino acid sequence analyzed. Its activity was tested by hemagglutination assay and carbohydrate-binding specificity determined by glycan microarray analysis. Its effect on proliferation of several human cell lines was determined by MTS assay.Results
A homodimeric lectin with 15.9-kDa subunits agglutinates human group A, followed by B, O, and bovine erythrocytes. Hemagglutination was inhibited by glycoprotein asialofetuin and lactose. Glycan microarray analysis revealed that the lectin recognizes human blood group A determinant GalNAcα1–3(Fucα1–2)Galβ-containing carbohydrates, and GalNAcβ1–4GlcNAc (N,N'-diacetyllactosediamine). The lectin exerts antiproliferative activity specific to human leukemic T cells.Conclusions
The protein belongs to the ricin B-like lectin superfamily, and has been designated as C. nebularis lectin (CNL). Its antiproliferative effect appears to be elicited by binding to carbohydrate receptors on human leukemic T cells.General significance
CNL is one of the few mushroom ricin B-like lectins that have been identified and the only one so far shown to possess immunomodulatory properties. 相似文献15.
Francisco J. Corpas Marina Leterrier Juan C. Begara-Morales Raquel Valderrama Mounira Chaki Javier López-Jaramillo Francisco Luque José M. Palma María N. Padilla Beatriz Sánchez-Calvo Capilla Mata-Pérez Juan B. Barroso 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Protein tyrosine nitration is a post-translational modification (PTM) mediated by nitric oxide-derived molecules. Peroxisomes are oxidative organelles in which the presence of nitric oxide (NO) has been reported.Methods
We studied peroxisomal nitroproteome of pea leaves by high-performance liquid chromatography with tandem mass spectrometry (LC–MS/MS) and proteomic approaches.Results
Proteomic analysis of peroxisomes from pea leaves detected a total of four nitro-tyrosine immunopositive proteins by using an antibody against nitrotyrosine. One of these proteins was found to be the NADH-dependent hydroxypyruvate reductase (HPR). The in vitro nitration of peroxisomal samples caused a 65% inhibition of HPR activity. Analysis of recombinant peroxisomal NADH-dependent HPR1 activity from Arabidopsis in the presence of H2O2, NO, GSH and peroxynitrite showed that the ONOO− molecule caused the highest inhibition of activity (51% at 5 mM SIN-1), with 5 mM H2O2 having no inhibitory effect. Mass spectrometric analysis of the nitrated recombinant HPR1 enabled us to determine that, among the eleven tyrosine present in this enzyme, only Tyr-97, Tyr-108 and Tyr-198 were exclusively nitrated to 3-nitrotyrosine by peroxynitrite. Site-directed mutagenesis confirmed Tyr198 as the primary site of nitration responsible for the inhibition on the enzymatic activity by peroxynitrite.Conclusion
These findings suggest that peroxisomal HPR is a target of peroxynitrite which provokes a loss of function.General significance
This is the first report demonstrating the peroxisomal NADH-dependent HPR activity involved in the photorespiration pathway is regulated by tyrosine nitration, indicating that peroxisomal NO metabolism may contribute to the regulation of physiological processes under no-stress conditions. 相似文献16.
Santosh Kumar Sahu Gopala Krishna Aradhyam Sathyanarayana N. Gummadi 《Biochimica et Biophysica Acta (BBA)/General Subjects》2009
Background
Phospholipid scramblases are a group of four homologous proteins conserved from C. elegans to human. In human, two members of the scramblase family, hPLSCR1 and hPLSCR3 are known to bring about Ca2+ dependent translocation of phosphatidylserine and cardiolipin respectively during apoptotic processes. However, affinities of Ca2+/Mg2+ binding to human scramblases and conformational changes taking place in them remains unknown.Methods
In the present study, we analyzed the Ca2+ and Mg2+ binding to the calcium binding motifs of hPLSCR1–4 and hPLSCR1 by spectroscopic methods and isothermal titration calorimetry.Results
The results in this study show that (i) affinities of the peptides are in the order hPLSCR1 > hPLSCR3 > hPLSCR2 > hPLSCR4 for Ca2+ and in the order hPLSCR1 > hPLSCR2 > hPLSCR3 > hPLSCR4 for Mg2+, (ii) binding of ions brings about conformational change in the secondary structure of the peptides. The affinity of Ca2+ and Mg2+ binding to protein hPLSCR1 was similar to that of the peptide I. A sequence comparison shows the existence of scramblase-like motifs among other protein families.Conclusions
Based on the above results, we hypothesize that the Ca2+ binding motif of hPLSCR1 is a novel type of Ca2+ binding motif.General significance
Our findings will be relevant in understanding the calcium dependent scrambling activity of hPLSCRs and their biological function. 相似文献17.
Hideyo Takatsuki Elina BengtssonAlf Månsson 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Bundles of unipolar actin filaments (F-actin), cross-linked via the actin-binding protein fascin, are important in filopodia of motile cells and stereocilia of inner ear sensory cells. However, such bundles are also useful as shuttles in myosin-driven nanotechnological applications. Therefore, and for elucidating aspects of biological function, we investigate if the bundle tendency to follow straight paths (quantified by path persistence length) when propelled by myosin motors is directly determined by material properties quantified by persistence length of thermally fluctuating bundles.Methods
Fluorescent bundles, labeled with rhodamine-phalloidin, were studied at fascin:actin molar ratios: 0:1 (F-actin), 1:7, 1:4 and 1:2. Persistence lengths (Lp) were obtained by fitting the cosine correlation function (CCF) to a single exponential function: < cos(θ(0) − θ(s)) > = exp(−s / (2Lp)) where θ(s) is tangent angle; s: path or contour lengths. < > denotes averaging over filaments.Results
Bundle-Lp (bundles < 15 μm long) increased from ~ 10 to 150 μm with increased fascin:actin ratio. The increase was similar for path-Lp (path < 15 μm), with highly linear correlation. For longer bundle paths, the CCF-decay deviated from a single exponential, consistent with superimposition of the random path with a circular path as suggested by theoretical analysis.Conclusions
Fascin–actin bundles have similar path-Lp and bundle-Lp, both increasing with fascin:actin ratio. Path-Lp is determined by the flexural rigidity of the bundle.General significance
The findings give general insight into mechanics of cytoskeletal polymers that interact with molecular motors, aid rational development of nanotechnological applications and have implications for structure and in vivo functions of fascin–actin bundles. 相似文献18.
Valdecir F. Ximenes Adriano S. PessoaCamila Z. Padovan Daniele C. AbrantesFabiana Helena F. Gomes Michele A. MaticoliManoel L. de Menezes 《Biochimica et Biophysica Acta (BBA)/General Subjects》2009
Background
Melatonin is well-established as a powerful reducing agent of oxidant generated in the cell medium. We aimed to investigate how readily melatonin is oxidized by peroxyl radicals ROO⋅ generated by the thermolysis of 2,2′-azobis(2-amidinopropane) hydrochloride (AAPH) and the role of glutathione (GSH) during the reaction course.Methods
Chromatographic, mass spectroscopy, and UV–visible spectrometric techniques were used to study the oxidation of melatonin by ROO⋅ or horseradish peroxidase (HRP)/H2O2. Our focus was the characterization of products and the study of features of the reaction.Results
We found that N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and a monohydroxylated derivative of melatonin were the main products of the reaction between melatonin and ROO⋅. Higher pH or saturation of the medium with molecular oxygen increased the yield of AFMK but did not affect the reaction rate. Melatonin increased the depletion of intracellular GSH mediated by AAPH. Using the HRP/H2O2 as the oxidant system, the addition of melatonin promoted the oxidation of GSH to GSSG.Conclusions
These results show, for the first time, that melatonin radical is able to oxidize GSH.General significance
We propose that this new property of melatonin could explain or be related to the recently reported pro-oxidant activities of melatonin. 相似文献19.
20.
Frederick J. Warren Peter J. ButterworthPeter R. Ellis 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013