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181.
Shixin Yang Lucian Barbu-Tudoran Marek Orzechowski Roger Craig John Trinick Howard White William Lehman 《Biophysical journal》2014,106(4):855-864
Muscle contraction is regulated by troponin-tropomyosin, which blocks and unblocks myosin binding sites on actin. To elucidate this regulatory mechanism, the three-dimensional organization of troponin and tropomyosin on the thin filament must be determined. Although tropomyosin is well defined in electron microscopy helical reconstructions of thin filaments, troponin density is mostly lost. Here, we determined troponin organization on native relaxed cardiac muscle thin filaments by applying single particle reconstruction procedures to negatively stained specimens. Multiple reference models led to the same final structure, indicating absence of model bias in the procedure. The new reconstructions clearly showed F-actin, tropomyosin, and troponin densities. At the 25 Å resolution achieved, troponin was considerably better defined than in previous reconstructions. The troponin density closely resembled the shape of troponin crystallographic structures, facilitating detailed interpretation of the electron microscopy density map. The orientation of troponin-T and the troponin core domain established troponin polarity. Density attributable to the troponin-I mobile regulatory domain was positioned where it could hold tropomyosin in its blocking position on actin, thus suggesting the underlying structural basis of thin filament regulation. Our previous understanding of thin filament regulation had been limited to known movements of tropomyosin that sterically block and unblock myosin binding sites on actin. We now show how troponin, the Ca2+ sensor, may control these movements, ultimately determining whether muscle contracts or relaxes. 相似文献
182.
Martin Hofrichter René Ullrich Marek J. Pecyna Christiane Liers Taina Lundell 《Applied microbiology and biotechnology》2010,87(3):871-897
Heme-containing peroxidases secreted by fungi are a fascinating group of biocatalysts with various ecological and biotechnological
implications. For example, they are involved in the biodegradation of lignocelluloses and lignins and participate in the bioconversion
of other diverse recalcitrant compounds as well as in the natural turnover of humic substances and organohalogens. The current
review focuses on the most recently discovered and novel types of heme-dependent peroxidases, aromatic peroxygenases (APOs),
and dye-decolorizing peroxidases (DyPs), which catalyze remarkable reactions such as peroxide-driven oxygen transfer and cleavage
of anthraquinone derivatives, respectively, and represent own separate peroxidase superfamilies. Furthermore, several aspects
of the “classic” fungal heme-containing peroxidases, i.e., lignin, manganese, and versatile peroxidases (LiP, MnP, and VP),
phenol-oxidizing peroxidases as well as chloroperoxidase (CPO), are discussed against the background of recent scientific
developments. 相似文献
183.
Christiane Liers Caroline Bobeth Marek Pecyna René Ullrich Martin Hofrichter 《Applied microbiology and biotechnology》2010,85(6):1869-1879
The jelly fungus Auricularia auricula-judae produced an enzyme with manganese-independent peroxidase activity during growth on beech wood (∼300 U l−1). The same enzymatic activity was detected and produced at larger scale in agitated cultures comprising of liquid, plant-based
media (e.g. tomato juice suspensions) at levels up to 8,000 U l−1. Two pure peroxidase forms (A. auricula-judae peroxidase (AjP I and AjP II) could be obtained from respective culture liquids by three chromatographic steps. Spectroscopic
and electrophoretic analyses of the purified proteins revealed their heme and peroxidase nature. The N-terminal amino acid
sequence of AjP matched well with sequences of fungal enzymes known as “dye-decolorizing peroxidases”. Homology was found
to the N-termini of peroxidases from Marasmius scorodonius (up to 86%), Thanatephorus cucumeris (60%), and Termitomyces albuminosus (60%). Both enzyme forms catalyzed not only the conversion of typical peroxidase substrates such as 2,6-dimethoxyphenol and
2,2′-azino-bis(3-ethylthiazoline-6-sulfonate) but also the decolorization of the high-redox potential dyes Reactive Blue 5
and Reactive Black 5, whereas manganese(II) ions (Mn2+) were not oxidized. Most remarkable, however, is the finding that both AjPs oxidized nonphenolic lignin model compounds (veratryl
alcohol; adlerol, a nonphenolic β-O-4 lignin model dimer) at low pH (maximum activity at pH 1.4), which indicates a certain ligninolytic activity of dye-decolorizing
peroxidases. 相似文献
184.
Kowalewski R Malkowski A Gacko M Sobolewski K 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》2010,48(4):542-548
Extensive extracellular matrix remodeling of the vein wall is involved in varicose veins pathogenesis. This process is controlled by numerous factors, including peptide growth factors. The aim of the study was to evaluate influence of thrombophlebitis on TGF-β1 and its signaling pathway in the vein wall. TGF-β1 mRNAlevels, growth factor content and its expression were evaluated by RT-PCR, ELISA, and western blot methods, respectively, in the walls of normal veins, varicose veins and varicose veins complicated by thrombophlebitis. Western blot analysis was used to assess TGF-β receptor type II (TGF-β RII) and p-Smad2/3 protein expression in the investigated material. Unchanged mRNA levels of TGF-β1, decreased TGF-β1 content, as well as decreased expression of latent and active forms of TGF-β1 were found in varicose veins. Increased expression of TGF-β RII and p-Smad2/3 were found in varicose veins. Thrombophlebitis led to increased protein expression of the TGF-β1 active form and p-Smad2/3 in the vein wall compared to varicose veins. TGF-β1 may play a role in the disease pathogenesis because of increased expression and activation of its receptor in the wall of varicose veins. Thrombophlebitis accelerates activation of TGF-β1 and activity of its receptor in the varicose vein wall. 相似文献
185.
Agrawal AK Ekonjo GB Teterycz E Zyoeko D Grzebieniak Z Milan M Marek G Siewiński M 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》2010,48(3):323-327
Cysteine proteinases and their inhibitors probably play the main role in carcinogenesis and metastasis. The metastasis process need external proteolytic activities that pass several barriers which are membranous structures of the connective tissue which includes, the basement membrane of blood vessels. Activities of the proteinases are regulated by endogenous inhibitors and activators. The imbalance between cysteine proteinases and cystatins seems to be associated with an increase in metastatic potential in some tumors. It has also been reported that proteinase inhibitors, specific antibodies for these enzymes and inhibition of the urokinase receptor may prevent cancer cell invasion. Some proteinase inhibitor could serve as agents for cancer treatment. 相似文献
186.
Ornithine-δ-aminotransferase (OAT, EC 2.6.1.13) catalyzes the transamination of l-ornithine to l-glutamate-γ-semialdehyde. The physiological role of OAT in plants is not yet well understood. It is probably related to arginine catabolism resulting in glutamate but the enzyme has also been associated with stress-induced proline biosynthesis. We investigated the enzyme from pea (PsOAT) to assess whether diamines and polyamines may serve as substrates or they show inhibitory properties. First, a cDNA coding for PsOAT was cloned and expressed in Escherichia coli to obtain a recombinant protein with a C-terminal 6xHis tag. Recombinant PsOAT was purified under native conditions by immobilized metal affinity chromatography and its molecular and kinetic properties were characterized. Protein identity was confirmed by peptide mass fingerprinting after proteolytic digestion. The purified PsOAT existed as a monomer of 50 kDa and showed typical spectral properties of enzymes containing pyridoxal-5′-phosphate as a prosthetic group. The cofactor content of PsOAT was estimated to be 0.9 mol per mol of the monomer by a spectrophotometric analysis with phenylhydrazine. l-Ornithine was the best substrate (Km = 15 mM) but PsOAT also slowly converted Nα-acetyl-l-ornithine. In these reactions, 2-oxoglutarate was the exclusive amino group acceptor (Km = 2 mM). The enzyme had a basic optimal pH of 8.8 and displayed relatively high temperature optimum. Diamines and polyamines were not accepted as substrates. On the other hand, putrescine, spermidine and others represented weak non-competitive inhibitors. A model of the molecular structure of PsOAT was obtained using the crystal structure of human OAT as a template. 相似文献
187.
Song JK Kannan R Merdes G Singh J Mlodzik M Giniger E 《Development (Cambridge, England)》2010,137(21):3719-3727
Abl is an essential regulator of cell migration and morphogenesis in both vertebrates and invertebrates. It has long been speculated that the adaptor protein Disabled (Dab), which is a key regulator of neuronal migration in the vertebrate brain, might be a component of this signaling pathway, but this idea has been controversial. We now demonstrate that null mutations of Drosophila Dab result in phenotypes that mimic Abl mutant phenotypes, both in axon guidance and epithelial morphogenesis. The Dab mutant interacts genetically with mutations in Abl, and with mutations in the Abl accessory factors trio and enabled (ena). Genetic epistasis tests show that Dab functions upstream of Abl and ena, and, consistent with this, we show that Dab is required for the subcellular localization of these two proteins. We therefore infer that Dab is a bona fide component of the core Abl signaling pathway in Drosophila. 相似文献
188.
David Gela Martin Kocour Martin Flajšhans Otomar Linhart Marek Rodina 《Reviews in Fish Biology and Fisheries》2010,20(3):301-306
A triennial performance test of five groups of tench, Tinca tinca (L.): Vodnany induced triploid V3n, Vodnany meiotic gynogenic Vgyn, diploid Vodnany V2n, Hungarian H2n and German G2n) in pond
monoculture was carried out with diploid golden tench as control (C) to compute corrected weight of the groups tested. Survival
rate ranged from 11.6% (V2n) to 30.6% (Vgyn) in yearlings, from 71.2% (V2n) to 91.5% (H2n) in 2 year-olds, from 60.0% (Vgyn)
to 75.7% (V2n) in 3 year-olds while that of the control group was 8.5, 38.3 and 40.2% in the respective seasons. After three
growing seasons the corrected weight of the fish in the groups H2n (254.6bg), V3n (257.0cg) and G2n (371.4cg) was higher (P < 0.05, Tukey HSD test) than that from the C (183.3ag) and V2n(205.6abg) groups. Among the chromosomally manipulated groups, ANCOVA test found the least slaughtering value for Vgyn (84.3%); among
the purebreds the highest value was found for H2n (87.32%), significantly differing from V2n and G2n strains. A high gonadosomatic
index in females (2.94 vs. 0.44% in males) resulted in inferior slaughtering values. 相似文献
189.
Martin Flajšhans David Gela Martin Kocour Hana Buchtová Marek Rodina Martin Pšenička Vojtěch Kašpar Veronika Piačková Eliška Sudová Otomar Linhart 《Reviews in Fish Biology and Fisheries》2010,20(3):317-329
Performance and physiological traits and health of spontaneous and induced triploid tench are reviewed. Triploidy is best
induced with cold shock; with triploids exhibiting 13.5–51.5% better weight gain, 2.69–3.94% higher slaughtering value, 20–60%
lower gonadosomatic index, 0.9–4.5% higher dry matter in flesh and up to 107% more flesh fat than diploids, if farmed untill
post sexual maturity. Triploids exhibit more abdominal fat and less polyunsaturated fatty acids of the n-3 and n-6 groups
in the flesh. Triploid females are sterile, while triploid males may produce aneuploid spermatozoa with varying DNA content
(1–1.9n) which may initiate development of embryos. Triploids have milder seasonal dynamics in their erythrocyte profile than
the diploids. Thinner diffusion distance in gills of triploids than in diploids is interpreted as adaptation to lower aerobic
capacity. Triploids show neither stronger tendencies to anatomic malformations, nor have bigger affinity to parasitic diseases
than the diploids. Production of triploid tench could be an economically interesting method of farming to higher marketable
weight, bringing a relatively high product quality. 相似文献
190.
Marek Sanak Anna GieliczKrzysztof Nagraba Marek KaszubaJagoda Kumik Andrew Szczeklik 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(21):1796-1800