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81.
Miguel López-Estepa Ana Ardá Martin Savko Adam Round William E. Shepard Marta Bruix Miquel Coll Francisco J. Fernández Jesús Jiménez-Barbero M. Cristina Vega 《PloS one》2015,10(4)
Cyclic N6-threonylcarbamoyladenosine (‘cyclic t6A’, ct6A) is a non-thiolated hypermodification found in transfer RNAs (tRNAs) in bacteria, protists, fungi and plants. In bacteria and yeast cells ct6A has been shown to enhance translation fidelity and efficiency of ANN codons by improving the faithful discrimination of aminoacylated tRNAs by the ribosome. To further the understanding of ct6A biology we have determined the high-resolution crystal structures of CsdL/TcdA in complex with AMP and ATP, an E1-like activating enzyme from Escherichia coli, which catalyzes the ATP-dependent dehydration of t6A to form ct6A. CsdL/TcdA is a dimer whose structural integrity and dimer interface depend critically on strongly bound K+ and Na+ cations. By using biochemical assays and small-angle X-ray scattering we show that CsdL/TcdA can associate with tRNA with a 1:1 stoichiometry and with the proper position and orientation for the cyclization of t6A. Furthermore, we show by nuclear magnetic resonance that CsdL/TcdA engages in transient interactions with CsdA and CsdE, which, in the latter case, involve catalytically important residues. These short-lived interactions may underpin the precise channeling of sulfur atoms from cysteine to CsdL/TcdA as previously characterized. In summary, the combination of structural, biophysical and biochemical methods applied to CsdL/TcdA has afforded a more thorough understanding of how the structure of this E1-like enzyme has been fine tuned to accomplish ct6A synthesis on tRNAs while providing support for the notion that CsdA and CsdE are able to functionally interact with CsdL/TcdA. 相似文献
82.
C. A. Arce Marta E. Hallak J. A. Rodriguez H. S. Barra R. Caputio 《Journal of neurochemistry》1978,31(1):205-210
Abstract— Incorporation of [14 C]tyrosine into the C-terminal position of α-tubulin of rat brain cytosol was 10-fold higher for non-assembled than for assembled tubulin. The incorporation into tubulin from disassembled microtubules was higher than into non-assembled tubulin; therefore, the low incorporation into microtubules was not due to a lower acceptor capacity of their tubulin constituent.
[14 C]Tyrosine was released from assembled and non-assembled [14 C]tyrosinated tubulin by the action of an endogenous carboxypeptidase. Release from non-assembled tubulin was shown by incubating a tubulinyl-[14 C]tyrosine preparation in the presence of CaCl2 at a concentration that abolished microtubule formation. Release from microtubules was inferred from the observation that the percentages of [14 C]tyrosine released and the decrease of the specific radioactivity of the recovered microtubules were practically identical and did not change after a 10-fold dilution of the incubated microtubules.
[3 H]Phenylalanine was released from a preparation of tubulinyl-[3 H]phenylalanine also by an enzymatic activity.
The capacity of a tubulin preparation to incorporate tyrosine was increased 43% by pre-treatment with endogenous carboxypeptidase.
Tubulin tyrosinated in vitro was assembled to the same extent as native tubulin. After a mixture of tubulinyl-[14 C]tyrosine and tubulinyl-[3 H]phenylalanine was partially assembled, the ratio of 14 C/3 H found in the microtubules was the same as in the non-assembled tubulin fraction. 相似文献
[
[
The capacity of a tubulin preparation to incorporate tyrosine was increased 43% by pre-treatment with endogenous carboxypeptidase.
Tubulin tyrosinated in vitro was assembled to the same extent as native tubulin. After a mixture of tubulinyl-[
83.
Günther Klonner Johannes Wessely Andreas Gattringer Dietmar Moser Iwona Dullinger Karl Hülber Sabine B. Rumpf Svenja Block Oliver Bossdorf Marta Carboni Luisa Conti Wayne Dawson Emily Haeuser Martin Hermy Tamara Münkemüller Madalin Parepa Wilfried Thuiller Sebastiaan Van der Veken Kris Verheyen Mark van Kleunen Franz Essl Stefan Dullinger 《Ecography》2019,42(9):1548-1557
Climate warming is supposed to enlarge the area climatically suitable to the naturalization of alien garden plants in temperate regions. However, the effects of a changing climate on the spread of naturalized ornamentals have not been evaluated by spatially and temporarily explicit range modelling at larger scales so far. Here, we assess how climate change and the frequency of cultivation interactively determine the spread of 15 ornamental plants over the 21st century in Europe. We coupled species distribution modelling with simulations of demography and dispersal to predict range dynamics of these species in annual steps across a 250 × 250 m raster of the study area. Models were run under four scenarios of climate warming and six levels of cultivation intensity. Cultivation frequency was implemented as size of the area used for planting a species. Although the area climatically suitable to the 15 species increases, on average, the area predicted to be occupied by them in 2090 shrinks under two of the three climate change scenarios. This contradiction obviously arises from dispersal limitations that were pronounced although we assumed that cultivation is spatially adapting to the changing climate. Cultivation frequency had a much stronger effect on species spread than climate change, and this effect was non‐linear. The area occupied increased sharply from low to moderate levels of cultivation intensity, but levelled off afterwards. Our simulations suggest that climate warming will not necessarily foster the spread of alien garden plants in Europe over the next decades. However, climatically suitable areas do increase and hence an invasion debt is likely accumulating. Restricting cultivation of species can be effective in preventing species spread, irrespective of how the climate develops. However, for being successful, they depend on high levels of compliance to keep propagule pressure at a low level. 相似文献
84.
85.
CD8+ CD28- T regulatory lymphocytes inhibiting T cell proliferative and cytotoxic functions infiltrate human cancers 总被引:1,自引:0,他引:1
Filaci G Fenoglio D Fravega M Ansaldo G Borgonovo G Traverso P Villaggio B Ferrera A Kunkl A Rizzi M Ferrera F Balestra P Ghio M Contini P Setti M Olive D Azzarone B Carmignani G Ravetti JL Torre G Indiveri F 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(7):4323-4334
Tumor growth is allowed by its ability to escape immune system surveillance. An important role in determining tumor evasion from immune control might be played by tumor-infiltrating regulatory lymphocytes. This study was aimed at characterizing phenotype and function of CD8+ CD28- T regulatory cells infiltrating human cancer. Lymphocytes infiltrating primitive tumor lesion and/or satellite lymph node from a series of 42 human cancers were phenotypically studied and functionally analyzed by suppressor assays. The unprecedented observation was made that CD8+ CD28- T regulatory lymphocytes are almost constantly present and functional in human tumors, being able to inhibit both T cell proliferation and cytotoxicity. CD4+ CD25+ T regulatory lymphocytes associate with CD8+ CD28- T regulatory cells so that the immunosuppressive activity of tumor-infiltrating regulatory T cell subsets, altogether considered, may become predominant. The infiltration of regulatory T cells seems tumor related, being present in metastatic but not in metastasis-free satellite lymph nodes; it likely depends on both in situ generation (via cytokine production) and recruitment from the periphery (via chemokine secretion). Collectively, these results have pathogenic relevance and implication for immunotherapy of cancer. 相似文献
86.
In vivo and in vitro effects of boron on the plasma membrane proton pump of sunflower roots 总被引:3,自引:0,他引:3
Marta Roldán rés Belver Pilar Rodríguez-Rosales Nuria Ferrol Juan Pedro Donaire 《Physiologia plantarum》1992,84(1):49-54
The effect of boron excess and deficiency on H+ efflux from excised roots from sunflower ( Heliarahus annuus L. cv. Enano) seedlings and on plasma membrane H+ -ATPase (EC 3.6.1.35) in isolated KI-washed microsomes has been investigated. When seedlings were grown in media with toxic levels of H3 BO3 (5 m M ) or without added boron and exposed to light conditions, an inhibition of the capacity for external acidification by excised roots was observed as compared to roots from seedlings grown with optimal H3 BO3 concentration (0.25 m M ). Toxic and deficient boron conditions also inhibited the vanadate-sensitive H+ -ATPase of microsomes isolated from the roots. The mechanism of boron toxicity was investigated in vitro with microsorne vesicles. A strong effect of boron on the vanadate-sensitive, ATP-dependent H+ transport was found, but the vanadate-sensitive phospho-bydrolase activity was not affected. These results suggest that boron could exert an effect on the plasma membrane properties, directly or indirectly regulating, proton transport. 相似文献
87.
We studied the aggregation state of Photosystem II in stacked and unstacked thylakoid membranes from spinach after a quick
and mild solubilization with the non-ionic detergent n-dodecyl-α,D-maltoside, followed by analysis by diode-array-assisted gel filtration chromatography and electron microscopy.
The results suggest that Photosystem II (PS II) isolates either as a paired, appressed membrane fragment or as a dimeric PS
II-LHC II supercomplex upon mild solubilization of stacked thylakoid membranes or PS II grana membranes, but predominantly
as a core monomer upon mild solubilization of unstacked thylakoid membranes. Analysis of paired grana membrane fragments reveals
that the number of PS II dimers is strongly reduced in single membranes at the margins of the grana membrane fragments. We
suggest that unstacking of thylakoid membranes results in a spontaneous disintegration of the PS II-LHC II supercomplexes
into separated PS II core monomers and peripheral light-harvesting complexes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
88.
Meacci E Cencetti F Donati C Nuti F Farnararo M Kohno T Igarashi Y Bruni P 《Biochimica et biophysica acta》2003,1633(3):133-142
The bioactive lipid sphingosine 1-phosphate (S1P) is known to exert powerful biological effects through the interaction with various members of the endothelial differentiation gene (EDG) receptor family, recently renamed S1P receptors. In the present study, evidence is provided that differentiation of C2C12 myoblasts into myotubes was accompanied by profound changes of EDG/S1P receptor expression. Indeed, in differentiated cells a significant increase of EDG3/S1P3 together with a large decrease of EDG5/S1P2 expression at mRNA as well as protein level was detected. Moreover, S1P was capable to initiate the signalling pathways downstream to cytosolic Ca(2+) increase in myotubes, similarly to that observed in myoblasts, whereas the signalling of the bioactive lipid to phospholipase D (PLD), but not that of bradykinin (BK) or lysophosphatidic acid (LPA), was found impaired in differentiated cells. Intriguingly, overexpression of EDG5/S1P2, but not EDG1/S1P1 or EDG3/S1P3, potentiated the efficacy of S1P to stimulate PLD, strongly suggesting a role for EDG5/S1P2 in the signalling to PLD. This view was also supported by the marked reduction of S1P-induced PLD activity in myoblasts loaded with antisense oligodeoxyribonucleotides (ODN) to EDG5/S1P2. Furthermore, overexpression of EDG5/S1P2 rescued the coupling of S1P signalling to PLD in C2C12 myotubes. Experimental evidence here provided supports the notion that EDG5/S1P2 plays a dominant role in the coupling of S1P to PLD in myoblasts and that the down-regulation of the receptor subtype is responsible for the specific uncoupling of S1P signalling to PLD in myotubes. 相似文献
89.
Collecting and storing biological material from wild animals in a way that does not deteriorate DNA quality for subsequent analyses is instrumental for research in ecology and evolution. Our aims were to gather reports on the effectiveness of methods commonly used by researchers for the field collection and long‐term storage of blood samples and DNA extracts from wild birds. Personal experiences were collected with an online survey targeted specifically at researchers sampling wild birds. Many researchers experienced problems with blood sample storage but not with DNA extract storage. Storage issues generated problems with obtaining adequate DNA quality and sufficient DNA quantity for the targeted molecular analyses but were not related to season of blood sampling, access to equipment, transporting samples, temperature, and method of blood storage. Final DNA quality and quantity were also not affected by storage time before DNA extraction or the methods used to extract DNA. We discuss practical aspects of field collection and storage and provide some general recommendations, with a list of pros and cons of different preservation methods of avian blood samples and DNA extracts. 相似文献
90.
Begoa Monterroso Miguel ngel Robles-Ramos Marta Sobrinos-Sanguino Juan Romn Luque-Ortega Carlos Alfonso William Margolin Germn Rivas Silvia Zorrilla 《Open biology》2023,13(3)
Cytokinesis is a fundamental process for bacterial survival and proliferation, involving the formation of a ring by filaments of the GTPase FtsZ, spatio-temporally regulated through the coordinated action of several factors. The mechanisms of this regulation remain largely unsolved, but the inhibition of FtsZ polymerization by the nucleoid occlusion factor SlmA and filament stabilization by the widely conserved cross-linking protein ZapA are known to play key roles. It was recently described that FtsZ, SlmA and its target DNA sequences (SlmA-binding sequence (SBS)) form phase-separated biomolecular condensates, a type of structure associated with cellular compartmentalization and resistance to stress. Using biochemical reconstitution and orthogonal biophysical approaches, we show that FtsZ-SlmA-SBS condensates captured ZapA in crowding conditions and when encapsulated inside cell-like microfluidics microdroplets. We found that, through non-competitive binding, the nucleotide-dependent FtsZ condensate/polymer interconversion was regulated by the ZapA/SlmA ratio. This suggests a highly concentration-responsive tuning of the interconversion that favours FtsZ polymer stabilization by ZapA under conditions mimicking intracellular crowding. These results highlight the importance of biomolecular condensates as concentration hubs for bacterial division factors, which can provide clues to their role in cell function and bacterial survival of stress conditions, such as those generated by antibiotic treatment. 相似文献