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151.
Nitrate reductase (NR, NADH:nitrate oxidoreductase, EC 1.6.6.1) from barley (Hordeum vulgare L. cv. Hassan) leaves was inactivated during a light-dark transition, losing approx. 50% of activity after 30 min of darkness. The dark inactivation was reversed by illumination of the seedlings, the kinetics of reactivation being similar to those of inactivation. High extractable NR activity and significant differences between illuminated and darkened leaves were observed in media containing EDTA and inorganic phosphate (Pi). Addition of Ca2+ ions during extraction and assay decreased NR activity from illuminated and darkened leaves, enhancing the light-dark difference. While no clear correlation could be found between irradiance and NR activity, a hyperbolic correlation appeared between extractable NR activity and in-vivo rates of CO2 fixation, indicating that NR activation follows saturation kinetics with respect to CO2 fixation. Furthermore, hexoses and hexose-phosphates fed to the leaves via the transpiration stream protected against the dark-inactivation of NR. The results indicate that carbon-assimilation products are regulatory factors of NR activity in barley leaves, mediating both the light-dark modulation of NR and its dependence upon CO2 fixation. 相似文献
152.
The influence of nitrate and ammonium assimilation on the flow of recently fixed carbon has been determined in intact Anacystis nidulans cells actively fixing CO2. Assimilation of nitrate or ammonium resulted in substantial increases in the incorporation of carbon into acid-soluble metabolites,
the magnitude of the effect being dependent on the irradiance. The radiolabel in sugar phosphate was virtually unaffected
by nitrogen assimilation, whereas that in organic acids and, in particular, in amino acids was markedly increased. Enhancement
of carbon incorporation into amino acids induced by nitrogen assimilation was not accompanied by parallel increases in the
size of the amino acid pools. This resulted in an appreciable increase of the specific radioactivity of most amino acids under
conditions of nitrogen assimilation. The data indicate that nitrate and ammonium assimilation induce an enhancement of carbon
flow through the glycolytic and the tricarboxylic-acid pathways to oxaloacetate and α-ketoglutarate, as well as a stimulation
of amino-acid turnover. These effects were more pronounced at saturating irradiance.
We thank the Dirección General de Investigación Científica y Técnica, Spain (research grant PB88-0019) and the Plan Andaluz
de Investigación (grupo 3101) for financial support, and P. Pérez de León for excellent secretarial assistance. 相似文献
153.
Mikkel W Pedersen Catia Antunes Binia De Cahsan J Víctor Moreno-Mayar Martin Sikora Lasse Vinner Darren Mann Pavel B Klimov Stuart Black Catalina Teresa Michieli Henk R Braig M Alejandra Perotti 《Molecular biology and evolution》2022,39(2)
Over the past few decades, there has been a growing demand for genome analysis of ancient human remains. Destructive sampling is increasingly difficult to obtain for ethical reasons, and standard methods of breaking the skull to access the petrous bone or sampling remaining teeth are often forbidden for curatorial reasons. However, most ancient humans carried head lice and their eggs abound in historical hair specimens. Here we show that host DNA is protected by the cement that glues head lice nits to the hair of ancient Argentinian mummies, 1,500–2,000 years old. The genetic affinities deciphered from genome-wide analyses of this DNA inform that this population migrated from north-west Amazonia to the Andes of central-west Argentina; a result confirmed using the mitochondria of the host lice. The cement preserves ancient environmental DNA of the skin, including the earliest recorded case of Merkel cell polyomavirus. We found that the percentage of human DNA obtained from nit cement equals human DNA obtained from the tooth, yield 2-fold compared with a petrous bone, and 4-fold to a bloodmeal of adult lice a millennium younger. In metric studies of sheaths, the length of the cement negatively correlates with the age of the specimens, whereas hair linear distance between nit and scalp informs about the environmental conditions at the time before death. Ectoparasitic lice sheaths can offer an alternative, nondestructive source of high-quality ancient DNA from a variety of host taxa where bones and teeth are not available and reveal complementary details of their history. 相似文献
154.
155.
Kilpatrick ED Terajima M Koster FT Catalina MD Cruz J Ennis FA 《Journal of immunology (Baltimore, Md. : 1950)》2004,173(5):3297-3304
Infection with lesion-derived Leishmania mexicana amastigotes inhibited LPS-induced IL-12 production by mouse bone marrow-derived macrophages. This effect was associated with expression of cysteine peptidase B (CPB) because amastigotes of CPB deletion mutants had limited ability to inhibit IL-12 production, whereas preincubation of cells with a CPB inhibitor, cathepsin inhibitor IV, was able to suppress the effect of wild-type amastigotes. Infection with wild-type amastigotes resulted in a time-dependent proteolytic degradation of IkappaBalpha and IkappaBbeta and the related protein NF-kappaB. This effect did not occur with amastigotes of CPB deletion mutants or wild-type promastigotes, which do not express detectable CPB. NF-kappaB DNA binding was also inhibited by amastigote infection, although nuclear translocation of cleaved fragments of p65 NF-kappaB was still observed. Cysteine peptidase inhibitors prevented IkappaBalpha, IkappaBbeta, and NF-kappaB degradation induced by amastigotes, and recombinant CPB2.8, an amastigote-specific isoenzyme of CPB, was shown to degrade GST-IkappaBalpha in vitro. LPS-mediated IkappaBalpha and IkappaBbeta degradation was not affected by these inhibitors, confirming that the site of degradation of IkappaBalpha, IkappaBbeta, and NF-kappaB by the amastigotes was not receptor-driven, proteosomal-mediated cleavage. Infection of bone marrow macrophages with amastigotes resulted in cleavage of JNK and ERK, but not p38 MAPK, whereas preincubation with a cysteine peptidase inhibitor prevented degradation of these proteins, but did not result in enhanced protein kinase activation. Collectively, our results suggest that the amastigote-specific cysteine peptidases of L. mexicana are central to the ability of the parasite to modulate signaling via NF-kappaB and consequently inhibit IL-12 production. 相似文献
156.
Phosphorylation by protein kinase CK2 changes the DNA binding properties of the human chromatin protein DEK
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Kappes F Damoc C Knippers R Przybylski M Pinna LA Gruss C 《Molecular and cellular biology》2004,24(13):6011-6020
We have examined the posttranslational modification of the human chromatin protein DEK and found that DEK is phosphorylated by the protein kinase CK2 in vitro and in vivo. Phosphorylation sites were mapped by quadrupole ion trap mass spectrometry and found to be clustered in the C-terminal region of the DEK protein. Phosphorylation fluctuates during the cell cycle with a moderate peak during G(1) phase. Filter binding assays, as well as Southwestern analysis, demonstrate that phosphorylation weakens the binding of DEK to DNA. In vivo, however, phosphorylated DEK remains on chromatin. We present evidence that phosphorylated DEK is tethered to chromatin throughout the cell cycle by the un- or underphosphorylated form of DEK. 相似文献
157.
Normal hematopoiesis and inflammatory responses despite discrete signaling defects in Galpha15 knockout mice
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Davignon I Catalina MD Smith D Montgomery J Swantek J Croy J Siegelman M Wilkie TM 《Molecular and cellular biology》2000,20(3):797-804
Galpha15 activates phospholipase Cbeta in response to the greatest variety of agonist-stimulated heptahelical receptors among the four Gq class G-protein alpha subunits expressed in mammals. Galpha15 is primarily expressed in hematopoietic cells in fetal and adult mice. We disrupted the Galpha15 gene by homologous recombination in embryonic stem cells to identify its biological functions. Surprisingly, hematopoiesis was normal in Galpha15(-/-) mice, Galpha15(-/-) Galphaq(-/-) double-knockout mice (which express only Galpha11 in most hematopoietic cells), and Galpha11(-/-) mice, suggesting functional redundancy in Gq class signaling. Inflammatory challenges, including thioglycolate-induced peritonitis and infection with Trichinella spiralis, stimulated similar responses in Galpha15(-/-) adults and wild-type siblings. Agonist-stimulated Ca(2+) release from intracellular stores was assayed to identify signaling defects in primary cultures of thioglycolate-elicited macrophages isolated from Galpha15(-/-) mice. C5a-stimulated phosphoinositide accumulation and Ca(2+) release was significantly reduced in Galpha15(-/-) macrophages. Ca(2+) signaling was abolished only in mutant cells pretreated with pertussis toxin, suggesting that the C5a receptor couples to both Galpha15 and Galphai in vivo. Signaling evoked by other receptors coupled by Gq class alpha subunits appeared normal in Galpha15(-/-) macrophages. Despite discrete signaling defects, compensation by coexpressed Gq and/or Gi class alpha subunits may suppress abnormalities in Galpha15-deficient mice. 相似文献
158.
Bean plants, Phaseolus vulgaris L. cv. Contender, were grown in the spring and summer seasons to study the relationship between xylem Na+/Cl-, transpiration rate, and salt tolerance. Eight-day-old seedlings were transplanted to 50% modified Hoagland solution with 1 mM NaCl. Four days after transfer, one of two treatments was applied: a control of 1 mM NaCl or a treatment of 25 mM NaCl every two days to reach a final treatment concentration of 75 mM NaCl. Plants were sampled on the fourth day after the final salt concentration was reached, eight days after the salinisation treatment began. Relative growth rate was 2.6-fold greater in summer than in spring. However, while no differences were found between treatments in spring, summer salt-treated plants had growth rates that were 31% lower than those of controls. In summer, CO2 assimilation, stomatal conductance, and transpiration rate of salinised plants declined with respect to controls. Leaf Na+ and trifoliolate leaf Cl- were higher in salt-treated plants in summer, although root Na+ was significantly higher in spring. Moreover, in summer salinity inhibited Ca2+ and K+ uptake and changed its distribution. Summer salt-treated plants had an average of 17-fold higher xylem Na+ during the daily cycle, while xylem Cl-, only in the afternoon, showed higher values (1.5-fold) compared to spring-grown plants. Our results suggest that the faster growth response to salt in summer-grown bean was at least partly due to an increase in xylem Na+ independent of the transpiration rate and possibly related to an increase in xylem Na+ influx or/and Na+ recirculation. 相似文献
159.
Timing of fission in the fissiparous starfish Allostichaster capensis under laboratory conditions is described. A. capensis generally splits across the disc along the fission plane during the spring, and then each half regenerates the missing arms during the rest of the year. The fission process can last eight hours. The healing process starts immediately after fission. A. capensis has impressive regeneration ability, including a comet, without signs of disc, regenerated two new arms. 相似文献
160.
Sun Jae Yoo Jacques Meyer Catalina Achim James Peterson Michael P. Hendrich E. Münck 《Journal of biological inorganic chemistry》2000,5(4):475-487
Rubredoxins contain a mononuclear iron tetrahedrally coordinated by four cysteinyl sulfurs. We have studied the wild-type protein from Clostridium pasteurianum and two mutated forms, C9S and C42S, in the oxidized and reduced states, with Mössbauer, integer-spin EPR, and magnetic circular dichroism (MCD) spectroscopies. The Mössbauer spectra of the ferric C42S and C9S mutant forms yielded zero-field splittings, D=1.2?cm?1, that are about 40% smaller than the D-value of the wild-type protein. The 57Fe hyperfine coupling constants were found to be ca. 8% larger than those of the wild-type proteins. The present study also revealed that the ferric wild-type protein has δ=0.24±0.01?mm/s at 4.2?K rather than δ=0.32?mm/s as reported in the literature. The Mössbauer spectra of both dithionite-reduced mutant proteins revealed the presence of two ferrous forms, A and B. These forms have isomer shifts δ=0.79?mm/s at 4.2?K, consistent with tetrahedral Fe2+(Cys)3(O-R) coordination. The zero-field splittings of the two forms differ substantially; we found D=?7±1?cm?1, E/D=0.09 for form A and D=+6.2±1.3?cm?1, E/D=0.15 for form B. Form A exhibits a well-defined integer-spin EPR signal; from studies at X- and Q-band we obtained g z =2.08±0.01, which is the first measured g-value for any ferrous rubredoxin. It is known from X-ray crystallographic studies that ferric C42S rubredoxin is coordinated by a serine oxygen. We achieved 75% reduction of C42S rubredoxin by irradiating an oxidized sample at 77?K with synchrotron X-rays; the radiolytic reduction produced exclusively form A, suggesting that this form represents a serine-bound Fe2+ site. Studies in different buffers in the pH?6–9 range showed that the A:B ratios, but not the spectral parameters of A and B, are buffer dependent, but no systematic variation of the ratio of the two forms with pH was observed. The presence of glycerol (30–50% v/v) was found to favor the B form. Previous absorption and circular dichroism studies of reduced wild-type rubredoxin have suggested d-d bands at 7400, 6000, and 3700?cm?1. Our low-temperature MCD measurements place the two high-energy transitions at ca. 5900 and 6300?cm?1; a third d-d transition, if present, must occur with energy lower than 3300?cm?1. The mutant proteins have d-d transitions at slightly lower energy, namely 5730, 6100?cm?1 in form A and 5350, 6380?cm?1 in form B. 相似文献