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61.
Invasive cane toads are unique in shape but overlap in ecological niche compared to Australian native frogs
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Invasive species are an important issue worldwide but predicting invasiveness, and the underlying mechanisms that cause it, is difficult. There are several primary hypotheses to explain invasion success. Two main hypothesis based on niche spaces stand out as alternative, although not exclusive. The empty niche hypothesis states that invaders occupy a vacant niche space in the recipient community, and the niche competition hypothesis states that invaders overlap with native species in niche space. Studies on trait similarity/dissimilarity between the invader and native species can provide information on their niche overlap. Here, we use the highly invasive and well‐studied cane toad (Rhinella marina) to test these two hypotheses in Australia, and assess its degree of overlap with native species in several niche dimensions. We compare extensive morphological and environmental data of this successful invader to 235 species (97%) of native Australian frogs. Our study is the first to document the significant morphological differences between the invasive cane toad and a continent‐wide frog radiation: despite significant environmental overlap, cane toads were distinct in body size and shape from most Australian frog species, suggesting that in addition to their previously documented phenotypic plasticity and wide environmental and trophic niche breadth, their unique shape also may have contributed to their success as an invasive species in Australia. Thus, the invasive success of cane toads in Australia may be explained through them successfully colonizing an empty niche among Australian anurans. Our results support that the cane toad's distinct morphology may have played a unique role in the invasiveness of this species in Australia, which coupled with a broad environmental niche breadth, would have boosted their ability to expand their distribution across Australia. We also propose RLLR (Relative limb length ratio) as a potentially useful measure of identifying morphological niche uniqueness and a potential measure of invasiveness potential in anuran amphibians. 相似文献
62.
Vitaly A Selivanov Pedro Vizán Faustino Mollinedo Teresa WM Fan Paul WN Lee Marta Cascante 《BMC systems biology》2010,4(1):135
Background
Metabolic flux profiling based on the analysis of distribution of stable isotope tracer in metabolites is an important method widely used in cancer research to understand the regulation of cell metabolism and elaborate new therapeutic strategies. Recently, we developed software Isodyn, which extends the methodology of kinetic modeling to the analysis of isotopic isomer distribution for the evaluation of cellular metabolic flux profile under relevant conditions. This tool can be applied to reveal the metabolic effect of proapoptotic drug edelfosine in leukemia Jurkat cell line, uncovering the mechanisms of induction of apoptosis in cancer cells. 相似文献63.
64.
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
65.
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-[
66.
Influence of organic co-solvents on the activity and substrate specificity of feruloyl esterases 总被引:1,自引:0,他引:1
Organic co-solvents can expand the use of enzymes in lignocellulose deconstruction through making substrates more soluble and thus more accessible. In choosing the most adequate co-solvent for feruloyl esterases, hydrolysis of methyl p-hydroxycinnamates by three pure enzymes (and a multi-enzyme preparation) was evaluated. Low concentrations of dimethylsulfoxide (DMSO) enhanced hydrolysis by two of the enzymes while at levels >20%, activity was reduced. DMSO also enhanced acetyl esterase-type activity of the enzymes. The co-solvent effect was different for each enzyme-substrate couple, indicating that other factors are also involved. Kinetic studies with a Talaromyces stipitatus feruloyl esterase showed low concentrations of dimethylsulfoxide enhanced the hydrolytic rate while Km also increased. Moreover, long-term incubation (96 h) of an Aspergillus niger feruloyl esterase in dimethylsulfoxide:water provided to the enzyme the ability to hydrolyze methyl p-coumarate, suggesting an active-site re-arrangement. Dimethylsulfoxide (10-30%) is proposed as an adequate co-solvent for feruloyl esterase treatment of water-insoluble substrates. 相似文献
67.
68.
Attempts to improve hematopoietic reconstitution and engraftment potential of ex vivo-expanded hematopoietic stem and progenitor cells (HSPCs) have been largely unsuccessful due to the inability to generate sufficient stem cell numbers and to excessive differentiation of the starting cell population. Although hematopoietic stem cells (HSCs) will rapidly expand after in vivo transplantation, experience from in vitro studies indicates that control of HSPC self-renewal and differentiation in culture remains difficult. Protocols that are based on hematopoietic cytokines have failed to support reliable amplification of immature stem cells in culture, suggesting that additional factors are required. In recent years, several novel factors, including developmental factors and chemical compounds, have been reported to affect HSC self-renewal and improve ex vivo stem cell expansion protocols. Here, we highlight early expansion attempts and review recent development in the extrinsic control of HSPC fate in vitro. 相似文献
69.
Bioactive conformations of two seminal delta opioid receptor penta‐peptides inferred from free‐energy profiles
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Delta‐opioid (DOP) receptors are members of the G protein‐coupled receptor (GPCR) sub‐family of opioid receptors, and are evolutionarily related, with homology exceeding 70%, to cognate mu‐opioid (MOP), kappa‐opioid (KOP), and nociceptin opioid (NOP) receptors. DOP receptors are considered attractive drug targets for pain management because agonists at these receptors are reported to exhibit strong antinociceptive activity with relatively few side effects. Among the most potent analgesics targeting the DOP receptor are the linear and cyclic enkephalin analogs known as DADLE (Tyr‐D ‐Ala‐Gly‐Phe‐D ‐Leu) and DPDPE (Tyr‐D ‐Pen‐Gly‐Phe‐D ‐Pen), respectively. Several computational and experimental studies have been carried out over the years to characterize the conformational profile of these penta‐peptides with the ultimate goal of designing potent peptidomimetic agonists for the DOP receptor. The computational studies published to date, however, have investigated only a limited range of timescales and used over‐simplified representations of the solvent environment. We provide here a thorough exploration of the conformational space of DADLE and DPDPE in an explicit solvent, using microsecond‐scale molecular dynamics and bias‐exchange metadynamics simulations. Free‐energy profiles derived from these simulations point to a small number of DADLE and DPDPE conformational minima in solution, which are separated by relatively small energy barriers. Candidate bioactive forms of these peptides are selected from identified common spatial arrangements of key pharmacophoric points within all sampled conformations. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 21–27, 2014. 相似文献
70.