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281.
Fusako Kawai 《FEMS microbiology letters》1985,30(3):273-276
Abstract Diglycolic acid dehydrogenase activity linked with 2,6-dichlorophenolindophenol and phenazine methosulfate was found in the particulate fraction of the cell-free extract of a mixed culture of Flavobacterium and Pseudomonas species grown on polyethylene glycol 6000. The amount of glyoxylic acid formed increased with the increase in reaction time and enzyme concentration. Horse heart cytochrome c , 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl 2H-tetrazolium bromide, and nitro blue tetrazolium, served as hydrogen acceptors in the presence of phenazine methosulfate. Enzyme activity was competitively inhibited by 1,4-benzoquinone. The enzyme was also active on tetraethylene glycol dicarboxylic acid, a metabolite of tetraethylene glycol, and on methoxy- or ethoxyacetic acid. 相似文献
282.
In order to examine germination characters, seedling parameters, water relative content, tolerance index and enzyme activities of seven Hungarian wheat landraces varieties (Tiszadadai, Riscsei, Komloi, Leweucei, Mateteleki, Mikebudai and Nyiradi) under five concentrations of water stress (0, 6, 12, 18, and 24%) of polyethylene glycol (PEG-6000). A laboratory experiment has been conducted through Factorial Experiment in Randomized Complete Block Design (RCBD) with four repetitions at Research Institute of Nyiregyhaza, Hungary. From the obtained results, Leweucei variety was surpassed other studied verities under study and recorded the highest values of all studied characters followed by Mateteleki, Komloi, Nyiradi, Riscsei, Tiszadadai and Mikebudai. Increasing water stress (PEG-6000) from 0 to 6, 12, 18 and 24% significantly reduced germination characters, seedlings parameters, water relative content (WRC), tolerance index and α and β-amylases activities. Generally, under water stress condition, Leweucei and Mateteleki varieties were recorded the highest values of water relative content (WRC), tolerance index (TI) and α and β-amylases activities as well as able to prompt better drought tolerance and could be suggested as a good resource for breeding programs and cultivation under drought stress conditions compared with other wheat landraces varieties. 相似文献
283.
《Cryobiology》2018
Limbal stem cell (LSC) deficiency causes progressive loss of vision but may be treated by transplant of autologous LSCs. Cryopreservation has the potential to indefinitely extend the lifespan of LSCs allowing re-transplant in case of graft failure. In this study, we aimed to identify the optimal cryoprotectant and cryoprotectant concentration for LSC cultures. Suspension cultures derived from cadaveric corneoscleral rims were cooled to 4 °C with Me2SO, propylene glycol or ethylene glycol at a concentration of 5%, 10% or 15%. Cell tolerance was measured in terms of membrane integrity, colony-forming efficiency and alamarBlue® reduction. Increasing cryoprotectant concentration above 5% reduced membrane integrity, metabolism and colony-forming efficiency. Cryoprotectant choice did not significantly influence these characteristics. Cells demonstrating Side Population were maintained after cryopreservation with 5% propylene glycol in vapour phase liquid nitrogen for 1 week, indicating that cryopreservation of LSCs with relatively low cryoprotectant concentration (5%) has promise in low-temperature eye banking. 相似文献
284.
Chie Shibazaki Shigeki Arai Rumi Shimizu Morihisa Saeki Takayoshi Kinoshita Andreas Ostermann Tobias E. Schrader Yuzuru Kurosaki Tomoko Sunami Ryota Kuroki Motoyasu Adachi 《Journal of molecular biology》2018,430(24):5094-5104
Casein kinase 2 (CK2) has broad phosphorylation activity against various regulatory proteins, which are important survival factors in eukaryotic cells. To clarify the hydration structure and catalytic mechanism of CK2, we determined the crystal structure of the alpha subunit of human CK2 containing hydrogen and deuterium atoms using joint neutron (1.9 Å resolution) and X-ray (1.1 Å resolution) crystallography. The analysis revealed the structure of conserved water molecules at the active site and a long potential hydrogen bonding network originating from the catalytic Asp156 that is well known to enhance the nucleophilicity of the substrate OH group to the γ-phospho group of ATP by proton elimination. His148 and Asp214 conserved in the protein kinase family are located in the middle of the network. The water molecule forming a hydrogen bond with Asp214 appears to be deformed. In addition, mutational analysis of His148 in CK2 showed significant reductions by 40%–75% in the catalytic efficiency with similar affinity for ATP. Likewise, remarkable reductions to less than 5% were shown by corresponding mutations on His131 in death-associated protein kinase 1, which belongs to a group different from that of CK2. These findings shed new light on the catalytic mechanism of protein kinases in which the hydrogen bond network through the C-terminal domain may assist the general base catalyst to extract a proton with a link to the bulk solvent via intermediates of a pair of residues. 相似文献
285.
Satoru Shimada Marika Oosaki Ryoko Takahashi Shigefumi Uene Sachiko Yanagisawa Tomitake Tsukihara Kyoko Shinzawa-Itoh 《BBA》2018,1859(2):154-163
Large assemblies of respiratory chain complexes, known as supercomplexes, are present in the mitochondrial membrane in mammals and yeast, as well as in some bacterial membranes. The formation of supercomplexes is thought to contribute to efficient electron transfer, stabilization of each enzyme complex, and inhibition of reactive oxygen species (ROS) generation. In this study, mitochondria from various organisms were solubilized with digitonin, and then the solubilized complexes were separated by blue native PAGE (BN-PAGE). The results revealed a supercomplex consisting of complexes I, III, and IV in mitochondria from bovine and porcine heart, and a supercomplex consisting primarily of complexes I and III in mitochondria from mouse heart and liver. However, supercomplexes were barely detectable in Drosophila flight-muscle mitochondria, and only dimeric complex V was present. Drosophila mitochondria exhibited the highest rates of oxygen consumption and NADH oxidation, and the concentrations of the electron carriers, cytochrome c and quinone were higher than in other species. Respiratory chain complexes were tightly packed in the mitochondrial membrane containing abundant phosphatidylethanolamine with the fatty acid palmitoleic acid (C16:1), which is relatively high oxidation-resistant as compared to poly-unsaturated fatty acid. These properties presumably allow efficient electron transfer in Drosophila. These findings reveal the existence of a new mechanism of biological adaptation independent of supercomplex formation. 相似文献
286.
Eric A. Johnson Miranda M. Russo Dillon B. Nye Jamie L. Schlessman Juliette T.J. Lecomte 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(12):2660-2673
Background
The nuclear genome of Chlamydomonas reinhardtii encodes a dozen hemoglobins of the truncated lineage. Four of these, named THB1–4, contain a single ~130-residue globin unit. THB1, which is cytoplasmic and capable of nitric oxide dioxygenation activity, uses a histidine and a lysine as axial ligands to the heme iron. In the present report, we compared THB2, THB3, and THB4 to THB1 to gain structural and functional insights into algal globins.Methods
We inspected properties of the globin domains prepared by recombinant means through site-directed mutagenesis, electronic absorption, CD, and NMR spectroscopies, and X-ray crystallography.Results
Recombinant THB3, which lacks the proximal histidine but has a distal histidine, binds heme weakly. NMR data demonstrate that the recombinant domains of THB2 and THB4 coordinate the ferrous heme iron with the proximal histidine and a lysine from the distal helix. An X-ray structure of ferric THB4 confirms lysine coordination. THB1, THB2, and THB4 have reduction potentials between ?65 and ?100 mV, are capable of nitric oxide dioxygenation, are reduced at different rates by the diaphorase domain of C. reinhardtii nitrate reductase, and show different response to peroxide treatment.Conclusions
Three single-domain C. reinhardtii hemoglobins use lysine as a distal heme ligand in both Fe(III) and Fe(II) oxidation states. This common feature is likely related to enzymatic activity in the management of reactive oxygen species.General significance
Primary structure analysis of hemoglobins has limited power in the prediction of heme ligation. Experimental determination reveals variations in this essential property across the superfamily. 相似文献287.
聚乙二醇修饰对酶活性和稳定性的影响 总被引:2,自引:0,他引:2
杨缜 《生物化学与生物物理进展》1995,22(4):340-345
经氰尿酰氯和对硝基苯碳酸酯活化过的甲氧基聚乙二醇分别用来对枯草杆菌蛋白酶进行化学修饰.修饰后的酶在水溶液和有机溶剂中均保持活性.酶在水溶液里的kcat增加,Km不变.酶对温度和pH的稳定性都显著升高,但最佳反应温度不变. 相似文献
288.
J. Zhang V. K. Tiwari T. J. Golds N. W. Blackhall E. C. Cocking B. J. Mulligan J. B. Power M. R. Davey 《Plant Cell, Tissue and Organ Culture》1995,41(2):125-138
Cat gene expression has been investigated following PEG-mediated plasmid uptake into barley protoplasts. The uptake conditions optimised for transient expression were employed for stable transformation. Transformed protoplast-derived calli of the cvs. Dissa and Igri, were selected on medium containing G418 at 40 g ml–1 or kanamycin sulphate at 250 g ml–1. Absolute transformation frequencies of 28.9×10–5 and 21.3×10–5 were recorded for Dissa with kanamycin sulphate and G418 selection, respectively. The frequency for Igri was 11.5×10–5 with G418 selection. Antibiotic resistant protoplast-derived colonies expressed NPTII activity; Southern hybridisation confirmed integration of the nptII gene into barley genomic DNA.Abbreviations ABA
abscisic acid
- AC-CAP
acetylated chloramphenicol
- BAP
6-benzylaminopurine
-
cat
chloramphenicol acetyltransferase gene
- CAT
chloramphenicol acetyltransferase activity
- CaMV
cauliflower mosaic virus
- CAP
chloramphenicol, 2,4-d-2,4-dichlorophenoxyacetic acid
- GA3
gibberellic acid
- G418
Geneticin
-
gus
-glucuronidase gene
- HEPES
(N[2-hydroxyethyl] piperazine-N-[2-ethanesulphonic acid])
- IAA
indole acetic acid
- MES
2-N-morpholinoethane sulphonic acid
- NAA
-naphthaleneacetic acid
-
npt II
neomycin phosphotransferase gene
- NPTH
neomycin phosphotransferase activity
- PEG
polyethylene glycol
- SCV
settled cell volume 相似文献
289.
A new method for assessing the effects of test compounds on Nicotiana alata pollen tubes in culture is described. Pollen tubes grow from a cluster of grains placed beneath a thin layer of gelled medium
in which test substances are incorporated and from which evaporation is prevented by a covering layer of oil. Pollen tubes
can grow to 8 mm in length in 24 h, which corresponds to about 25% of the maximum growth rate in styles. Growth is non-destructively
measured. The developmental stages reached by cultured tubes are similar to those of tubes growing in styles; growth changes
from being reserve-dependent to reserve-independent, callose plugs form, and the nucleus of the generative cell divides. Because
culture volumes are small (10–20 μl per replicate), the effects of known concentrations of microgram quantities of compounds
on the growth of pollen tubes can be tested.
Received: 25 February 1997 / 21 July 1997 相似文献
290.
Tetraploid somatic hybrids were produced by protoplast fusion between Solanum brevidens, a diploid non-tuber-bearing wild species and a diploid tuber-bearing potato line derived from an S. tuberosum Gp. Phureja-Stenotumum population. S. brevidens has resistance to potato leaf roll virus (PLRV) and frost but is difficult to cross sexually with cultivated potato. Hybridity was verified by morphological characteristics and cytological observations. Nine of ten hybrids tested showed resistance to PLRV. Hybrids produced fertile pollen and eggs which may allow beneficial traits of S. brevidens to be incorporated into a conventional potato breeding programme. 相似文献