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991.
Mikel Latasa Renate Scharek Florence Le Gall Laure Guillou 《Journal of phycology》2004,40(6):1149-1155
Pigment analysis performed on 30 Prasinophyceae strains revealed two main groups: the prasinoxanthin‐containing and prasinoxanthin‐less Prasinophyceae. Prasinoxanthin‐containing Prasinophyceae comprised the orders Mamiellales, Pseudoscourfieldiales (Pycnococcaceae), and Prasinococcales. For this group, classification with pigment composition showed a good agreement with molecular phylogeny. Mamiellales, except Crustomastix stigmatica, accumulated uriolide, micromonal, dihydrolutein, and the pigment Unidentified M1 as characteristic pigments. Prasinococcales and Pseudoscourfieldiales (Pycnococcaceae) lacked micromonal and Unidentified M1. In addition, Pseudoscourfieldiales (Pycnococcaceae) lacked uriolide. A chl c3‐like pigment was present in prasinoxanthin‐containing strains isolated from the deep sea. Common green algae pigments, a loroxanthin derivative, and siphonaxanthin plus derivatives were found in the prasinoxanthin‐less Prasinophyceae, which included strains from Pyramimonadales, Pseudoscourfieldiales (Nephroselmidiaceae), Chlorodendrales, and a new order. Although some associations could be observed, the correspondence between pigments and molecular taxonomy was less clear for this group. 相似文献
992.
993.
Forcing expression of a soybean root glutamine synthetase gene in tobacco leaves induces a native gene encoding cytosolic enzyme 总被引:1,自引:0,他引:1
Bertrand Hirel Marie C. Marsolier Anne Hoarau Jackson Hoarau Judy Brangeon Renate Schafer Desh Pal S. Verma 《Plant molecular biology》1992,20(2):207-218
Glutamine synthetase (GS; EC 6.3.1.2) is present in different subcellular compartments in plants. It is located in the cytoplasm in root and root nodules while generally present in the chloroplasts in leaves. The expression of GS gene(s) is enhanced in root nodules and in soybean roots treated with ammonia. We have isolated four genes encoding subunits of cytosolic GS from soybean (Glycine max L. cv. Prize). Promoter analysis of one of these genes (GS15) showed that it is expressed in a root-specific manner in transgenic tobacco and Lotus corniculatus, but is induced by ammonia only in the legume background. Making the GS15 gene expression constitutive by fusion with the CaMV-35S promoter led to the expression of GS in the leaves of transgenic tobacco plants. The soybean GS was functional and was located in the cytoplasm in tobacco leaves where this enzyme is not normally present. Forcing this change in the location of GS caused concomitant induction of the mRNA for a native cytosolic GS in the leaves of transgenic tobacco. Shifting the subcellular location of GS in transgenic plants apparently altered the nitrogen metabolism and forced the induction in leaves of a native GS gene encoding a cytosolic enzyme. The latter is normally expressed only in the root tissue of tobacco. This phenomenon may suggest a hitherto uncharacterized metabolic control on the expression of certain genes in plants. 相似文献
994.
Christoph von Eichel-Streiber Rita Laufenberg-Feldmann Sabine Sartingen Jörg Schulze Markus Sauerborn 《Molecular & general genetics : MGG》1992,233(1-2):260-268
Summary The six clones pTB112, pTB324, pTBs12, pCd122, pCd14 and pCdl3 cover thetox locus ofClostridium difficile VPI 10463. This region of 19 kb of chromosomal DNA contains four open reading frames including the completetoxB andtoxA genes. The two toxins show 63% amino acid (aa) homology, a relatedness that had been predicted by the cross-reactivity of some monoclonal antibodies (mAb) but that is in contrast to the toxin specificity of polyclonal antisera. A special feature of ToxA and ToxB is their repetitive C-termini. We define herein 19 individual CROPS (combinedrepetitiveoligopeptides of 20–50 as length) in the ToxB C-terminus, which are separable into five homologous groups. Comparison of the as sequences of the N-terminal two-thirds of ToxA and ToxB revealed three marked structures, a cluster of 172 hydrophobic, highly conserved as in the centre of both toxins, a sequence of 120 residues with an accumulation of highly conserved arginine, cysteine, histidine, methionine, and tryptophan residues, and a stretch of 248 less conserved aa. The probable function of these domains is discussed. Structural and functional homologies of ToxA and ToxB indicate that both genes have a common ancestor and may have evolved by gene duplication, with subsequent recombination and mutation, as has been reported for streptococcal glucosyltransferases (Gtf). 相似文献
995.
The degradation of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) by insulin-degrading enzyme (IDE) has been investigated. As revealed by high-performance liquid chromatography, all three peptides are sequentially cleaved at a limited number of sites, the latter of which were identified by mass spectrometric analyses. The studies revealed that ANP is preferred as substrate over BNP and CNP. ANP degradation is rapidly initiated by hydrolysis at the Ser25-Phe26 bond. Three additional cleavage sites were identified in ANP after prolonged incubation with IDE; in contrast, three and two bonds were hydrolyzed in BNP and CNP, respectively. Analysis of the nine cleavage sites shows a preference for basic or hydrophobic amino acid residues on the carboxyl side of a cleaved peptide bond. In contrast to most of the peptide fragments generated by IDE activity, the initial ANP cleavage product, F-R-Y, is rapidly degraded further by cleavage of the R-Y bond. Cross-linking studies with 125I-ANP in the presence of sulfhydryl-modifying agent indicate that IDE activity is inhibited at the level of initial substrate binding whereas metal-ion chelating agents only prevent hydrolysis. On the basis of its structural and enzymatic properties, IDE exhibits striking similarity to a number of recently-described endopeptidases. 相似文献
996.
W. P. Quick K. Fichtner E. -D. Schulze R. Wendler R. C. Leegood H. Mooney S. R. Rodermel L. Bogorad M. Stitt 《Planta》1992,188(4):522-531
The effect of nitrogen supply during growth on the contribution of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco; EC 4.1.1.39) to the control of photosynthesis was examined in tobacco (Nicotiana tabacum L.). Transgenic plants transformed with antisense rbcS to produce a series of plants with a progressive decrease in the amount of Rubisco were used to allow the calculation of the flux-control coefficient of Rubisco for photosynthesis (CR). Several points emerged from the data: (i) The strength of Rubisco control of photosynthesis, as measured by CR, was altered by changes in the short-term environmental conditions. Generally, CR was increased in conditions of increased irradiance or decreased CO2. (ii) The amount of Rubisco in wild-type plants was reduced as the nitrogen supply during growth was reduced and this was associated with an increase in CR. This implied that there was a specific reduction in the amount of Rubisco compared with other components of the photosynthetic machinery. (iii) Plants grown with low nitrogen and which had genetically reduced levels of Rubisco had a higher chlorophyll content and a lower chlorophyll a/b ratio than wild-type plants. This indicated that the nitrogen made available by genetically reducing the amount of Rubisco had been re-allocated to other cellular components including light-harvesting and electron-transport proteins. It is argued that there is a luxury additional investment of nitrogen into Rubisco in tobacco plants grown in high nitrogen, and that Rubisco can also be considered a nitrogen-store, all be it one where the opportunity cost of the nitrogen storage is higher than in a non-functional storage protein (i.e. it allows for a slightly higher water-use efficiency and for photosynthesis to respond to temporarily high irradiance).Abbreviations CR
flux control coefficient of Rubisco for photosynthesis
-
rbcS
gene for the Rubisco small subunit
- Rubisco
ribulose-1,5-bisphosphate carboxylase-oxygenase
W.P. Quick is grateful to Professor D.T. Clarkson (Department of Agricultural Sciences, University of Bristol, Long Ashton, UK) for pointing out the connection between stomatal conductance and nutrient availability. This work was supported by the Deutsche Forschungsgemeinschaft. 相似文献
997.
Two chromosomal high mobility group (HMG) proteins from larvae of Chironomus thummi (Diptera) and from an epithelial cell line of Chironomus tentans were purified to homogeneity and chemically characterized. cDNA clones encoding these proteins were isolated from an expression library using an immunoscreening approach and were sequenced. The deduced amino acid sequences revealed their homology to HMG protein 1 of vertebrates. These insect proteins have therefore been designated cHMG1a and cHMG1b. They have a molecular mass of 12,915 and 12,019 kDa, respectively, and preferentially bind to AT-rich DNA. Indirect immunofluorescence microscopy with a polyclonal antibody showed the presence of cHMG1a and cHMG1b in condensed chromomeres but not in puffs, nucleoli, and cytoplasm. The cHMG1a and cHMG1b genes were both localized to a single band in region 14 of chromosome 1 of C. tentans and appear to be single copy genes. An immunologically related protein was purified from Drosophila melanogaster Kc cells. Its size and amino acid composition indicate that it is an HMG1 of D. melanogaster. On the other hand, our antibody did not recognize calf HMG1. The identification and characterization of HMG1 proteins in insects with polytene chromosomes opens new possibilities for studying function(s) of this group of chromosomal proteins. 相似文献
998.
Synthesis and secretion of hirudin by Streptomyces lividans 总被引:2,自引:0,他引:2
Eckhard Bender Renate Vogel Klaus-Peter Koller Joachim Engels 《Applied microbiology and biotechnology》1990,34(2):203-207
Summary To examine the secretory production of heterologous proteins by Streptomyces lividans, we fused the DNA encoding the signal peptide of the -amylase inhibitor tendamistat, derived from S. tendae with a synthetic gene encoding the thrombin inhibitor hirudin. The analysis of secretion by immunoblots revealed an efficient translocation of hirudin through the membrane, with no detectable immunoreaction among the cellular proteins. The secreted hirudin was stable in the shaking culture for about 6 days. A comparison of the hirudin secreted by S. lividans and recombinant reference hirudin from yeast by immunoblots and thrombin inhibition assays shows that hirudin from Streptomyces has a lower specific activity, which may be due to a different aminoterminal sequence or to inexact processing of the precursor.Offprint requests to: J. Engels 相似文献
999.
Prof. Dr. Rudolf Schulze 《Radiation and environmental biophysics》1974,11(1):21-30
Summary From investigations on the wavelength dependence of carcinogenic UV radiation one can conclude that the spectral efficiency for human skin cancer approximately corresponds to the spectral efficiency for erythema. On the basis of this assumption, so-called biological units were computed by analogy with the Finsen units. The computations were performed for several geographical latitudes and the different seasons. The result is: More than 70% of the carcinogenic UV radiation is received by the equatorial zone from 30 deg N to 30 deg S. Finally, the increase of UV radiation due to a possible decrease of ozone concentration by 1 mm and 0.5 mm STP, resp., as a consequence of stratospheric aircraft exhaust were computed. For the equatorial zone, a decrease from 3 mm O3 to 2 (2.5) mm O3 results in an UV increase by 79 (31) %. The increase of spectral irradiation due to decreasing ozone concentration was also computed.
Eingegangen am 7. Juni 1973
Herrn Prof. Dr. Drs. h. c. B. Rajewsky zum 80. Geburtstag gewidmet. 相似文献
Über die Zunahme der biologisch wirksamen ultravioletten Sonnenstrahlung bei Verminderung der Ozonkonzentration in der freien Erdatmosphäre
Zusammenfassung Ein Studium der Untersuchungen zur Frage der Wellenlängenabhängigkeit der karzinogenen UV-Strahlung stützte die Annahme, daß das Wirkungsspektrum für den menschlichen Hautkrebs der Erythemwirksamkeitskurve etwa entspricht. Von dieser Annahme ausgehend wurden in Analogie zur Berechnung der Finsen-Einheiten Biologische Einheiten für die verschiedenen geographischen Breiten in Abhängigkeit von den Jahreszeiten berechnet. Das Ergebnis lautet: mehr als 70% der karzinogenen UV-Strahlung entfällt auf die äquatoriale Zone (30°N-Äquator-30°S). Abschließend wurde geprüft, um wieviel die UV-Strahlung zunimmt, falls durch Flugzeugabgase in der Stratosphäre die Ozonkonzentration um 1 mm bzw. 0,5 mm abnimmt; für die äquatoriale Zone ergeben sich 79% Zunahme (3 mm O3 auf 2 mm O3) bzw. 31 % Zunahme (3 mm O3 auf 2,5 mm 03). Auch die Zunahme der Bestrahlungsstärken der einzelnen Wellenlängen bei Abnahme der Ozonkonzentration wurde berechnet.
Eingegangen am 7. Juni 1973
Herrn Prof. Dr. Drs. h. c. B. Rajewsky zum 80. Geburtstag gewidmet. 相似文献
1000.
Dr. Cornelia Schulze 《Cell and tissue research》1974,153(3):339-355
Summary As revealed by light microscopical investigations the human Sertoli cell presents different appearances according to the pattern of infranuclear cytoplasmic inclusions. Although two or three stages of spermatogenesis are seen in a single cross section of a seminiferous tubule the Sertoli cells all show virtually the same features in such a cross sectioned tubule.The different appearances are also evident under the electron microscope. Although no obvious correlation was found with the stages of spermatogenesis in the seminiferous epithelium, the Sertoli cell appearances described here may be assumed to represent different metabolic situations.Other features of Sertoli cell ultrastructure are discussed such as the presence of residual bodies in the apical cytoplasm, glycogen-rich areas protruding towards the tubular lumen or the extracellular space, and membrane bound, round structures, found between the membranes of the smooth endoplasmic reticulum and resembling the microbodies of steroid producing cells.Presented in part at the 69th Versammlung der Anatomischen Gesellschaft, Kiel, 1974. 相似文献