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1.
Summary The high molecular weight ribonucleic acids from the green algaDunaliella were isolated from wholeDunaliella cells and fromDunaliella ribosomes and analysed by the technique of sucrose density centrifugation. Ribonucleic acids from whole cells and fromDunaliella ribosomes showed the same sedimentation profile only when ribosomes were prepared in the presence of the RNase inhibitor polyvinyl sulfate. Otherwise ribonucleic acids fromDunaliella ribosomes were degraded to some extent, as compared with those from whole cells, although the ribosomes were still physically intact. The ribonucleic acids fromDunaliella were resolved by sucrose density centrifugation into three high molecular weight components sedimenting with 26, 23 and 17.5s. The 80s ribosomal fraction contained mainly a 26 and 17.5 s RNA, whereas the 50 s ribosomal fraction contained a 23 s RNA. The 26 s RNA and the 23 s RNA may represent the heavy ribonucleic acids from the cytosol and the chloroplast of the cell respectively, whereas the 17.5 s RNA may be a mixture of the two light RNA's from the two cell compartments.The experiments described in this paper were submitted by H. J.Rahmsdorf to the Fachbereich Biologie der Freien UniversitÄt Berlin in partial fulfillment of the requirements for a doctor's degree. 相似文献
2.
Wiebe Visser Edwin A. van Spronsen Nanne Nanninga Jack T. Pronk J. Gijs Kuenen Johannes P. van Dijken 《Antonie van Leeuwenhoek》1995,67(3):243-253
Effects of growth conditions on mitochondrial morphology were studied in livingSaccharomyces cerevisiae cells by vital staining with the fluorescent dye dimethyl-aminostyryl-methylpyridinium iodine (DASPMI), fluorescence microscopy, and confocal-scanning laser microscopy. Cells from respiratory, ethanol-grown batch cultures contained a large number of small mitochondria. Conversely, cells from glucose-grown batch cultures, in which metabolism was respiro-fermentative, contained small numbers of large, branched mitochondria. These changes did not significantly affect the fraction of the cellular volume occupied by the mitochondria. Similar differences in mitochondrial morphology were observed in glucose-limited chemostat cultures. In aerobic chemostat cultures, glucose metabolism was strictly respiratory and cells contained a large number of small mitochondria. Anaerobic, fermentative chemostat cultivation resulted in the large, branched mitochondrial structures also seen in glucose-grown batch cultures. Upon aeration of a previously anaerobic chemostat culture, the maximum respiratory capacity increased from 10 to 70 µmole.min–1.g weight–1 within 10 h. This transition resulted in drastic changes of mitochondrial number, morphology and, consequently, mitochondrial surface area. These changes continued for several hours after the respiratory capacity had reached its maximum. Cyanide-insensitive oxygen consumption contributed ca. 50% of the total respiratory capacity in anaerobic cultures, but was virtually absent in aerobic cultures. The response of aerobic cultures to oxygen deprivation was qualitatively the reverse of the response of anaerobic cultures to aeration. The results indicate that mitochondrial morphology inS. cerevisiae is closely linked to the metabolic activity of this yeast: conditions that result in repression of respiratory enzymes generally lead to the mitochondrial morphology observed in anaerobically grown, fermenting cells. 相似文献
3.
Nucleocapsids released from influenza virions by sodium deoxycholate sedimented heterogeneously in sucrose gradients. Highly infectious virus (complete) preparations yielded nucleocapsids with peak distributions at 64 and 56S; von Magnus type virus (incomplete) lacked 64S nucleocapsids. Treatment of influenza virus nucleocapsids with pancreatic ribonuclease rendered the associated viral ribonucleic acid (RNA) molecules acid-soluble, indicating that capsid proteins do not completely surround the viral RNA's. However, the capsid proteins remained associated after enzymatic hydrolysis of the RNA, as judged by persistently high sedimentation rates. Sedimentation rates of viral nucleocapsids reflected the sedimentation rates of the associated RNA's: 64S nucleocapsids contained 18S RNA, whereas 56S nucleocapsids contained 15S RNA, although in both cases RNA's sedimenting at 4 to 13S were also recovered. Furthermore, just as incomplete virions lacked 64S nucleocapsids, they also lacked 18S RNA. These findings support the hypothesis that the influenza virus genome is divided among several distinct pieces of RNA. 相似文献
4.
Ana M. Casas Andrzej K. Kononowicz Theresa G. Haan Lanying Zhang Dwight T. Tomes Ray A. Bressan Paul M. Hasegawa 《In vitro cellular & developmental biology. Plant》1997,33(2):92-100
Summary Transgenic sorghum plants (Sorghum bicolor L. Moench, cv. SRN39) were obtained by microprojectile-mediated DNA delivery (Bio-Rad PDS 1000/He Biolistic Delivery System)
to explants derived from immature inflorescences. Explants were precultured on medium supplemented with 2.5 mg/l (11.31 μM)
2,4-D, 0.5 mg/l (2.32 μM) kinetin, and 60 g/l sucrose for 1 to 2 wk prior to bombardment. Bialaphos selectron pressure was
imposed 2 wk after bombardment and maintained throughout all the culture stages leading to plant regeneration. More than 2500
explants from 1.5 to 3.0 cm inflorescences were bombarded and subjected to bialaphos selection. Out of more than 190 regenerated
plants, 5 were determined to be Ignite resistant. Southern analyses confirmed the likelihood that the 5 herbicide resistant
plants derived from two independent transformation events. The phosphinothricin acetyltransferase gene (bar) was inherited by and functionally expressed in T1 progeny. However, no β-glucuronidase (GUS) activity could be detected in T1 plants that contained uidA restriction fragments. Histological analyses indicated that in the absence of bialaphos morphogenesis was primarily via embryogenesis
while organogenesis was more predominant in callus maintained with herbicide selection. 相似文献
5.
Upon subfractionation of certain plant seed homogenates on sucrose density gradients, we encountered problems in defining
the location and amount of mitochondria using marker enzymes. In order to overcome the inherent limitations of enzyme assays,
we utilized a heterologous DNA probe specific foratp6 in maize orBrassica tournefortii to detect mitochondria. The samples were treated with SDS, proteinase K, and RNase A followed by agarose gel electrophoresis,
and blotting. The immobilized DNA was detected with [32P]-labelled probes, and quantified using a phosphor imager. The assay is specific, sensitive, and independent of species,
cell type, and developmental stage, thus circumventing the need for expressed protein to assay enzyme activity. 相似文献
6.
Cotyledon explants of immature ginseng zygotic embryos cultured on Murashige and Skoog medium lacking growth regulators formed
somatic embryos directly, most in a multiple state, fused together and to the parent cotyledon explants. When the cotyledon
explants of ginseng were pretreated with 1.0 m sucrose for 24–72 h, all the somatic embryos developed individually from all surfaces of the cotyledons and the number of
somatic embryos per explant was enhanced fourfold. Histological observation revealed that all the single somatic embryos from
preplasmolysed cotyledons originated from epidermal single cells, whereas all the multiple embryos from cotyledons without
pretreatment originated from epidermal and subepidermal cell masses. When the somatic embryos matured to the cotyledonary
stage, further growth ceased and they remained white, probably indicating dormancy. Gibberellic acid (GA3) (over 1.0 mg/l) or chilling treatment (–2°C for over 8 weeks) were prerequisites for the germination of somatic embryos.
Ultrastructural observation revealed that the cotyledon cells of somatic embryos without chilling or GA3 treatment contained numerous lipid reserves, dense cytoplasm, proplastids and non-activated mitochondria, whereas the cotyledon
cells of somatic embryos after chilling or GA3 treatment were highly vacuolated and contained well-developed chloroplasts and active-state mitochondria enclosing numerous
cristae, indicating that in-vitro-developed somatic embryos of P. ginseng may be dormant after maturing in a manner similar to zygotic embryos.
Received: 8 July 1998 / Revision received: 31 August 1998 / Accepted: 23 September 1998 相似文献
7.
Sucrose partitioning between vascular bundles and storage parenchyma in the sugarcane stem: a potential role for the ShSUT1 sucrose transporter 总被引:6,自引:0,他引:6
A transporter with homology to the SUT/SUC family of plant sucrose transporters was isolated from a sugarcane (Saccharum hybrid) stem cDNA library. The gene, designated ShSUT1, encodes a protein of 517 amino acids, including 12 predicted membrane-spanning domains and a large central cytoplasmic loop. ShSUT1 was demonstrated to be a functional sucrose transporter by expression in yeast. The estimated Km for sucrose of the ShSUT1 transporter was 2 mM at pH 5.5. ShSUT1 was expressed predominantly in mature leaves of sugarcane that were exporting sucrose and in stem internodes that were actively accumulating sucrose. Immunolocalization with a ShSUT1-specific antiserum identified the protein in cells at the periphery of the vascular bundles in the stem. These cells became lignified and suberized as stem development proceeded, forming a barrier to apoplasmic solute movement. However, the movement of the tracer dye, carboxyfluorescein from phloem to storage parenchyma cells suggested that symplasmic connections are present. ShSUT1 may have a role in partitioning of sucrose between the vascular tissue and sites of storage in the parenchyma cells of sugarcane stem internodes. 相似文献
8.
Traianos Yupsanis Petros S. Kefalas Phedra Eleftheriou Konstantinos Kotinis 《Journal of plant physiology》2001,158(7)
Nucleolytic activities from two plants of Leguminosae family were determined in order to consider if the nucleases of plants which belong to the same family or to the same species responded in similar ways to stress conditions during growth. Growth parameters of both plants were examined in parallel. In detail, seedlings from two plants, alfalfa (Medicago sativa L. cv. Luzerne Euver) and lentil (Lens culinaris cv. Thessalia), showed significant differences in response to iso-osmotic solutions of NaCl (100 mmol · L−1 solution equivalent to conductivity 8.0 dS m−1) and mannitol (190 mmol · kg−1). Plant height and dry weight of mannitol/NaCl-treated seeds in both plants were lower in comparison to controls (water). Mannitol stress reduced height and dry weight in alfalfa seedlings more than did NaCl. By contrast, lentil seedling growth was inhibited more by NaCl stress than mannitol. In addition, DNase and RNase response to mannitol stress differed in each plant compared to the controls. Mannitol stress induced a sharp increase in DNase- and RNase-specific activity during the initial stages of alfalfa seedlings' growth, followed by a decrease during subsequent days; in lentil seedlings, these activities were inhibited throughout the entire growth period. NaCl stress inhibited the above activities in both plants. After native electrophoresis on gels polymerized in the presence of DNA/RNA, the overall band intensities confirmed the above quantitative results of alfalfa RNase and DNase activity. In addition, the active gel analysis revealed that the decrease of nucleolytic activities in mannitol-treated alfalfa seedlings was mainly due to the strong reduction of acid nucleases. This is the first report of different non-ionic osmotic response of type I plant nucleases during seedlings' growth. In vitro, the addition of up to 300 mmol/L mannitol did not affect acid and neutral nuclease activity in enzyme preparations extracted, purified, and separated from control and mannitol-treated alfalfa seedlings.Our results suggest that plant nucleases responded in a different way to osmotic stress and ionic stress conditions during seedlings' growth. 相似文献
9.
Exudate was collected fromRicinus communis L. cotyledons after cutting the hypocotyl. It contained high levels of sucrose and potassium, a low level of calcium, and a pH of approx. 7.5. After application of [14C] sucrose to the cotyledons, radioactivity could be recovered from the exudate, indicating that the exudate was derived from the phloem. Using data from a number of individual seedlings, correlations between loading rates of sucrose, translocation rates, and sucrose and potassium contents were analyzed. A positive correlation was found between the rate of sucrose loading and the rate of sucrose exudation, whereas a negative correlation existed between the contents of sucrose and potassium in the phloem. 相似文献
10.
Understanding the present-day distribution of molecular variation requires knowledge about the history of the species. Past
colonization routes and locations of refugia of Scots pine (Pinus sylvestris) were inferred from variation in mitochondrial DNA in material collected from 37 populations located in countries within,
and immediately adjacent to the continent of Europe. Two mitochondrial regions, nad1 intron (exon B/C) and nad7 intron 1, were included in the study. Differentiation in maternally inherited mitochondria was high (G
ST′ = 0.824). Two new haplotypes were found at the nad7 intron 1. The occurrence of a 5-bp indel variant was restricted to the Turkish Kalabak population and a 32 bp only found
in Central, Eastern, and Northern Europe. The complete absence of the 32-bp indel from the Mediterranean peninsulas supports
the view that coniferous forests existed outside these areas during the last glacial maximum, and these populations contributed
to the subsequent colonization of the northern parts of Europe. P. sylvestris shares features of its glacial and postglacial history with two other northern, cold-tolerant tree species, Picea abies and Betula sp. These three species differ from many other European trees for which pollen core and molecular evidence indicate colonization
from southern refugia after the last glacial period. 相似文献
11.
Isolated epidermis of Commelina communis L. and Tulipa gesneriana L. assimilated 14CO2 into malic acid and its metabolites but not into sugars or their phosphates; epidermis could not reduce CO2 by photosynthesis and therefore must be heterotrophic (Raschke and Dittrich, 1977). If, however, isolated epidermis of Commelina communis was placed on prelabelled mesophyll (obtained by an exposure to 14CO2 for 10 min), radioactive sugars appeared in the epidermis, most likely by transfer from the mesophyll. Of the radioactivity in the epidermis, 60% was in sucrose, glucose, fructose, 3-phosphoglyceric acid and sugar phosphates. During a 10-min exposure to 14CO2, epidermis in situ incorporated 16 times more radioactivity than isolated epidermal strips. Isolated epidermis of Commelina communis and Tulipa gesneriana took up 14C-labelled glucose-1-phosphate (without dephosphorylation), glucose, sucrose and maltose. These substances were transformed into other sugars and, simultaneously, into malic acid. Carbons-1 through-3 of malic acid in guard cells can thus be derived from sugars. Radioactivity appeared also in the hydrolysate of the ethanol-insoluble residue and in compounds of the tricarboxylic-acid cycle, including their transamination products. The hydrolysate contained glucose as the only radioactive compound. Radioactivity in the hydrolysate was therefore considered an indication of starch. Starch formation in the epidermis began within 5 min of exposure to glucose-1-phosphate. Autoradiograms of epidermal sections were blackened above the guard cells. Formation of starch from radioactive sugars therefore occurred predominantly in these cells. Epidermis of tulip consistently incorporated more 14C into malic and aspartic acids than that of Commelina communis (e.g. after a 4-h exposure to [14C]glucose in the dark, epidermis, with open stomata, of tulip contained 31% of its radioactivity in malate and aspartate, that of Commelina communis only 2%). The results of our experiments allow a merger of the old observations on the involvement of starch metabolism in stomatal movement with the more recent recognition of ion transfer and acid metabolism as causes of stomatal opening and closing.Abbreviation G-1-P
glucose-1-phosphate 相似文献
12.
Till Jelitto Uwe Sonnewald Lothar Willmitzer Mohammad Hajirezeai Mark Stitt 《Planta》1992,188(2):238-244
Metabolite levels and carbohydrates were investigated in the leaves of tobacco (Nicotiana tabacum L.) and leaves and tubers of potato (Solanum tuberosum L.) plants which had been transformed with pyrophosphatase from Escherichia coli. In tobacco the leaves contained two- to threefold less pyrophosphate than controls and showed a large increase in UDP-glucose, relative to hexose phosphate. There was a large accumulation of sucrose, hexoses and starch, but the soluble sugars increased more than starch. Growth of the stem and roots was inhibited and starch, sucrose and hexoses accumulated. In potato, the leaves contained two- to threefold less pyrophosphate and an increased UDP-glucose/ hexose-phosphate ratio. Sucrose increased and starch decreased. The plants produced a larger number of smaller tubers which contained more sucrose and less starch. The tubers contained threefold higher UDP-glucose, threefold lower hexose-phosphates, glycerate-3-phosphate and phosphoenolpyruvate, and up to sixfold more fructose-2,6-bisphosphatase than the wild-type tubers. It is concluded that removal of pyrophosphate from the cytosol inhibits plant growth. It is discussed how these results provide evidence that sucrose mobilisation via sucrose synthase provides one key site at which pyrophosphate is needed for plant growth, but is certainly not the only site at which pyrophosphate plays a crucial role.Abbreviations Fru2,6bisP
fructose-2,6-bisphosphate
- Fru6P
fructose 6-phosphate
- FW
fresh weight
- Glc1P
glucose-1-phosphate
- Glc6P
glucose-6-phosphate
- PEP
phosphoenolpyruvate
- 3PGA
glycerate-3-phosphate
- PFK
phosphofructokinase
- PFP
pyrophosphate: fructose-6-phosphate phosphotransferase
- Pi
inorganic phosphate
- PPi
inorganic pyrophosphate
- UDPGlc
UDP-glucose
This research was supported by the Deutsche Forschungsgemein-Schaft (SFB 137) and Sandoz AG (T.J., M.H., M.S.) and by the Bundesminister für Forschung und Technologie (U.S., L.W.). 相似文献
13.
H. F. van Ark R. D. Hall J. Creemers-Molenaar F. A. Krens 《Plant Cell, Tissue and Organ Culture》1992,31(3):223-232
Methods for the isolation of cytoplasts from suspension culture-derived protoplasts of the monocot Lolium perenne (perennial ryegrass) and the dicot Beta vulgaris (sugarbeet) have been determined. After comparing a range of gradients it was found that a discontinuous sucrose/mannitol gradient gave the highest cytoplast yields for both species tested: of the protoplasts loaded onto the gradient, for Beta >30% and for Lolium up to 45% could be recovered as cytoplasts. Sufficient protoplasts could be loaded onto the gradient to produce suitable numbers of cytoplasts for use in asymmetric somatic hybridisation experiments. Cytoplasts could be isolated from several suspension cultures of different ages. The cytoplast fraction was recovered from the upper part of the gradient in all cases and was only slightly contaminated (2–8%) with protoplasts. Lolium cytoplasts were small, evacuolate cells with granular cytoplasm. In contrast, Beta cytoplasts were larger and predominantly vacuolate. Both contained mitochondria as determined using fluorescence staining.Abbreviations 2,4-d
2,4 dichlorophenoxyacetic acid
- M
mannitol
- S
sucrose
- P
Percoll
- S/M
sucrose/mannitol gradient 相似文献
14.
Partial purification and characterization of mitochondrial DNA polymerase from Plasmodium falciparum
Porntip Chavalitshewinkoon-Petmitr Srisucha Chawprom Lieve Naesens Jan Balzarini Prapon Wilairat 《Parasitology international》2000,49(4)
Mitochondria of chloroquine-resistant Plasmodium falciparum (K1 strain) were isolated from mature trophozoites by differential centrifugation. The mitochondrial marker enzyme cytochrome c reductase was employed to monitor the steps of mitochondria isolation. Partial purification of DNA polymerase from P. falciparum mitochondria was performed using fast protein liquid chromatography (FPLC). DNA polymerase of P. falciparum mitochondria was characterized as a γ-like DNA polymerase based on its sensitivity to the inhibitors aphidicolin, N-ethylmaleimide and 9-β-
-arabinofuranosyladenine-5′-triphosphate. In contrast, the enzyme was found to be strongly resistant to 2′,3′-dideoxythymidine-5′-triphosphate (IC50>400 μM) and differed in this aspect from the human homologue, possibly indicating structural differences between human and P. falciparum DNA polymerase γ. In addition, the DNA polymerase of parasite mitochondria was shown to be resistant (IC50>1 mM) to the nucleotide analogue (S)-1-[3-hydroxy-2-phosphonylmethoxypropyl]adenine diphosphate (HPMPApp). 相似文献
15.
Changying Zeng Fangsen Xu Yunhua Wang Chengxiao Hu Jinling Meng 《Plant and Soil》2007,296(1-2):187-196
Boron (B) is an essential micronutrient for higher plants, but the adaptability of plants to B deficiency varies widely both
between and within species. On the basis of quantitative trait loci (QTL) analysis of the B efficiency coefficient (BEC) detected
in an Arabidopsis thaliana Ler × Col recombinant inbred (RI) population, B efficiency was evaluated in the original parents (Ler and Col-4) and two F8 lines (1938 and 1961), both of which were selected on the basis of phenotype and genotype of the RI population. The parent
Ler and F8 progeny 1938 had higher BEC and B utilization efficiency (BUE) values than those calculated for parent Col-4 and F8 progeny 1961, respectively, when grown in nutrient solutions containing three different concentrations of B. The magnitude
of the BEC and BUE-values was correlated closely with the combined phenotypic effect of the corresponding QTLs among the four
genotypes. The F8 line, 1938, inherited all four B-efficient QTLs, AtBE1-1, AtBE1-2, AtBE2 and AtBE5, from its two original parents. The four QTLs accounted for 65.2% of the total variation in BEC and 1938 showed the highest
BEC (0.74) and BUE (10.5) values among the four genotypes when grown in nutrient solution that contained 0.324 μM B. Only
one minor-effect QTL (AtBE1-1) was found in the parent, Col-4. This QTL accounted only for 8.8% of total BEC variation and resulted in the lowest BEC (0.39)
and BUE (0.76) in Col-4 when it was grown in nutrient solution that contained 0.324 μM B. Phenotypic profile analysis showed
that 1938 not only inherited the B utilization and distribution characteristics found in the silique of Ler, but also acquired the low-B requirement for root and shoot growth from Col-4. As a result, this genotype displayed the strongest
tolerance to B deficiency. In addition, both B-efficient genotypes, 1938 and Ler, possessed the QTL (AtBE1-2) and both plants had high-seed yields and high-B distributions in their siliques. Therefore, we hypothesize that QTL AtBE1-2 plays a role in the utilization and/or the distribution of B to the silique when plants suffer from B deficiency. A close
correlation between the B-efficient phenotype and the corresponding QTLs indicated that phenotypic differences depend on the
genetic variation.
Responsible Editor: Richard W. Bell. 相似文献
16.
《Bioscience, biotechnology, and biochemistry》2013,77(12):1982-1988
The primary structure and base specificity of chicken liver RNase CL1 which has been reported by Miura et al. [Chem. Pharm. Bull., 32,4053–4060 (1984)] as poly U-preferential RNase, were extensively studied. The sequence study of this enzyme and comparison of the amino acid sequence of the enzyme with homologous RNases from oyster and Drosophila melanogaster suggested that RNase CL1 consists of three peptides with 17, 19, and 163 amino acid residues. The amino acid sequence of these three peptides were identified. The two small peptides are joined to the large peptide by disulfide bridges. The amino acid sequence of RNase CL1 had 62 (31.2%) and 63 residues (31.6%) identical with oyster RNase and D. melanogaster RNase, respectively, and belongs to the RNase T2 family RNase.Reassessment of the base specificity of RNase CL1 found that it is guanylic acid, then uridylic acid-preferential, and not poly U preferential. 相似文献
17.
The efficiency of any plant regeneration system lies in part in its wide applicability to diverse genotypes. In Asiatic Vigna, cotyledon and cotyledonary node explants from 4-day-old seedlings of 27 genotypes were cultured in a medium consisting of
MS salts, B5 vitamins, 3.0% sucrose and 1.0 mg l-1 BA. Direct and efficient multiple shoot regeneration (80–100%) from the cotyledonary nodes was obtained in all epigeal species
namely radiata, mungo, aconitifolia, subspecies radiata var. sublobata, mungo var. silvestris and in the hypogeal but allotetraploid glabrescens. In contrast, two other hypogeal species V. angularis and V. umbellata failed to initiate shoots from the nodes. However, adventititious shoots developed at the basipetal cut (hypocotyl) in 35–67%
of V. angularis explants. These results provide evidence in support of the existing genomic grouping within subgenus Ceratotropis, which designates AA, A1A1 and A1A1/- to epigeal, hypogeal and the allotetraploid species, respectively. Mean shoot production ranged from 3.3 to 10.4 shoots
per explant during the first subculture and varied significantly among the responsive genotypes within 4 species. Additional
shoots were obtained in all genotypes after subsequent subculture. However, cotyledons were not as regenerable as cotyledonary
node explants. Although significant differences in rooting were observed among the shoots of the 15 genotypes, the response
was generally higher in MS basal medium (MSO) than in MS with 1.0 mg l-1 IAA. Regenerated plants were successfully transferred to soil (50–100% survival rate) and all surviving plants were reproductively
fertile.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Addition of ethidium bromide to ameboid cultures of the slime mold,Dictyostelium discoideum, caused a cessation of cell division after 1 or 2 generations. The replication of mitochondrial DNA was immediately blocked as indicated by the 50% decrease in the DNA content of purified mitochondria from ethidium-bromide-treated cultures. The activity of the respiratory chain was also inhibited, resulting in a 75% decrease in cyanide-sensitive whole cell respiration. Spectral analysis at low temperature indicated that the amount of cytochromec
1 was decreased 80% and that of cytochromec increased 100% in mitochondria from treated cells. Two cytochromesb absorbing at 556 and 561 nm were observed in mitochondria from both control and ethidium-bromide-treated cultures. The content of cytochromeb
561 appeared to decline more than didb
556, but it is hard to quantitate the decrease. The effects of ethidium bromide were fully reversible. When the drug was removed, the cells resumed a normal growth rate without any discernible lag. The activity of oligomycin-sensitive ATPase, cytochrome oxidase, and succinate-cytochrome-c reductase as well as the cytochrome content began to increase after 1 day returning to control levels within 5 days. Electron micrographs of whole cells treated with ethidium bromide revealed that mitochondrial profiles were elongated and had greatly reduced cristae. Numerous membrane whorls were apparent, as was a profound loss of rough endoplasmic reticulum. Three days after removal of ethidium bromide, mitochondria were again ovoid in shape and contained well-developed cristae. In all of the cells during recovery, there was a single large vacuole that appeared to enclose a large portion of the cell volume, forming a new cellular compartment that may simplify the breakdown of previously damaged organelles.This work is in partial fulfillment of the requirements for the Doctor of Philosophy degree at the City University of New York. 相似文献
19.
《Bioscience, biotechnology, and biochemistry》2013,77(11):2437-2444
A Pichia pastoris expression system for bovine pancreatic RNase A was constructed: the RNase A sequence was fused to the PHO1 signal and the AOX1 promoter was used for efficient secretion. Approximately 5 mg of soluble enzymes were secreted per liter of the culture, but one half of them were glycosylated. After a series of purifications by cation-exchange chromatography, the glycosylated enzyme was removed and the pure recombinant soluble unglycosylated RNase A was obtained in the final yield of 1 mg per liter of the culture. N-Terminal sequence, molecular weight, secondary structure, thermal stability, and activity were completely identical with those of commercial RNase A. Glycosylated RNase A had a decreased k cat, 60-70% of the activity of wild-type RNase A, as in the case of RNase B. Its carbohydrate moiety seemed to destabilize the enzyme differently from RNase B since T m of the glycosylated RNase A was decreased by 6°C. The carbohydrate moiety of the glycosylated enzyme contained no GlcNAc. The N34A mutant RNase A, in which the only potential N-glycosylation site, Asn34, is mutated to alanine, was also glycosylated, implying that glycosylation is not N-linked but O-linked. 相似文献
20.
Summary Five peaks of RNA from bleached Euglena gracilis are resolved by polyacrylamide-gel electrophoresis. The extraction of these RNA's and their subsequent resolution on gels is dependent upon pH and the presence of an RNase inhibitor (e.g., macaloid). Careful control of ionic strength also appears necessary. Inorganic phosphate is incorporated first by low molecular weight RNA, then by a high molecular weight RNA (hRNA) and a peak with a sedimentation coefficient of 13S, and then by rRNA.The electrophoretic pattern of RNA from Astasia longa is similar to that of bleached Euglena whereas that from wild-type Euglena is more complex and presumably reflects the presence of chloroplast RNA's in these latter cells. 相似文献