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201.
Structural basis for antibacterial peptide self‐immunity by the bacterial ABC transporter McjD
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Valentina Corradi Kamel El Omari Armin Wagner Indran Mathavan Séverine Zirah Weixiao Yuan Wahlgren D Peter Tieleman Olav Schiemann Sylvie Rebuffat Konstantinos Beis 《The EMBO journal》2017,36(20):3062-3079
Certain pathogenic bacteria produce and release toxic peptides to ensure either nutrient availability or evasion from the immune system. These peptides are also toxic to the producing bacteria that utilize dedicated ABC transporters to provide self‐immunity. The ABC transporter McjD exports the antibacterial peptide MccJ25 in Escherichia coli. Our previously determined McjD structure provided some mechanistic insights into antibacterial peptide efflux. In this study, we have determined its structure in a novel conformation, apo inward‐occluded and a new nucleotide‐bound state, high‐energy outward‐occluded intermediate state, with a defined ligand binding cavity. Predictive cysteine cross‐linking in E. coli membranes and PELDOR measurements along the transport cycle indicate that McjD does not undergo major conformational changes as previously proposed for multi‐drug ABC exporters. Combined with transport assays and molecular dynamics simulations, we propose a novel mechanism for toxic peptide ABC exporters that only requires the transient opening of the cavity for release of the peptide. We propose that shielding of the cavity ensures that the transporter is available to export the newly synthesized peptides, preventing toxic‐level build‐up. 相似文献
202.
A review of the ecosystem functions in oil palm plantations,using forests as a reference system
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Alexander C. Keyel Jan Salecker Yael Kisel Katrin M. Meyer Mark Auliya Andrew D. Barnes Marife D. Corre Kevin Darras Heiko Faust Bastian Hess Stephan Klasen Alexander Knohl Holger Kreft Ana Meijide Fuad Nurdiansyah Fenna Otten Guy Pe'er Stefanie Steinebach Suria Tarigan Merja H. Tölle Teja Tscharntke Kerstin Wiegand 《Biological reviews of the Cambridge Philosophical Society》2017,92(3):1539-1569
Oil palm plantations have expanded rapidly in recent decades. This large‐scale land‐use change has had great ecological, economic, and social impacts on both the areas converted to oil palm and their surroundings. However, research on the impacts of oil palm cultivation is scattered and patchy, and no clear overview exists. We address this gap through a systematic and comprehensive literature review of all ecosystem functions in oil palm plantations, including several (genetic, medicinal and ornamental resources, information functions) not included in previous systematic reviews. We compare ecosystem functions in oil palm plantations to those in forests, as the conversion of forest to oil palm is prevalent in the tropics. We find that oil palm plantations generally have reduced ecosystem functioning compared to forests: 11 out of 14 ecosystem functions show a net decrease in level of function. Some functions show decreases with potentially irreversible global impacts (e.g. reductions in gas and climate regulation, habitat and nursery functions, genetic resources, medicinal resources, and information functions). The most serious impacts occur when forest is cleared to establish new plantations, and immediately afterwards, especially on peat soils. To variable degrees, specific plantation management measures can prevent or reduce losses of some ecosystem functions (e.g. avoid illegal land clearing via fire, avoid draining of peat, use of integrated pest management, use of cover crops, mulch, and compost) and we highlight synergistic mitigation measures that can improve multiple ecosystem functions simultaneously. The only ecosystem function which increases in oil palm plantations is, unsurprisingly, the production of marketable goods. Our review highlights numerous research gaps. In particular, there are significant gaps with respect to socio‐cultural information functions. Further, there is a need for more empirical data on the importance of spatial and temporal scales, such as differences among plantations in different environments, of different sizes, and of different ages, as our review has identified examples where ecosystem functions vary spatially and temporally. Finally, more research is needed on developing management practices that can offset the losses of ecosystem functions. Our findings should stimulate research to address the identified gaps, and provide a foundation for more systematic research and discussion on ways to minimize the negative impacts and maximize the positive impacts of oil palm cultivation. 相似文献
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Bożena Szal Agata Jastrzębska Marek Kulka Karolina Leśniak Anna Podgórska Tiit Pärnik Hiie Ivanova Olav Keerberg Per Gardeström Anna M. Rychter 《Planta》2010,232(6):1371-1382
The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state
on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no
effect on photosynthetic CO2 assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants. Impaired mitochondrial
respiratory chain activity was associated with the perturbation of mitochondrial TCA cycle manifested, e.g., by lowered decarboxylation
rate. Mitochondrial dysfunction in MSC16 plants had different influence on leaf cell metabolism under dark or light conditions.
In the dark, when the main mitochondrial function is the energy production, the altered activity of TCA cycle in mutated plants
was connected with the accumulation of pyruvate and TCA cycle intermediates (citrate and 2-OG). In the light, when TCA activity
is needed for synthesis of carbon skeletons required as the acceptors for NH4
+ assimilation, the concentration of pyruvate and TCA intermediates was tightly coupled with nitrate metabolism. Enhanced incorporation
of ammonium group into amino acids structures in mutated plants has resulted in decreased concentration of organic acids and
accumulation of Glu. 相似文献
205.
Neurotransmission requires proper organization of synaptic vesicle pools and rapid release of vesicle contents upon presynaptic depolarization. Genetic studies have begun to reveal a critical role for scaffolding proteins in such processes. Mutations in genes encoding components of the highly conserved MALS/CASK/Mint-1 complex cause presynaptic defects. In all three mutants, neurotransmitter release is reduced in a manner consistent with aberrant vesicle cycling to the readily releasable pool. Recently, liprin-alpha proteins, which define active zone size and morphology, were found to associate with MALS/CASK, suggesting that this complex links the presynaptic release machinery to the active zone, thereby regulating neurotransmitter release. 相似文献
206.
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208.
Sigvald B. Refsum Erling Håskjold Rolf Bjerknes Olav Hilmar Iversen 《Virchows Archiv. B, Cell pathology including molecular pathology》1991,60(1):225-230
The rat corneal epithelium has been chosen as a model for studying growth regulation. In this epithelium a large single cohort
of cells enters the S phase during a fairly short time period once a day. The factor responsible for this wave of cell proliferation
is unknown, but it may be a chemical signal from the central nervous system (the suprachiasmatic nucleus or the corpus pineale).
The mature cell compartment of the corneal epithelium is assumed to produce a negative feedback factor (chalone), counteracting
the effect of the circadian proliferative factor on the local cell proliferation. When no circadian factor is being produced,
during most of the 24 h, the chalone seems to enhance the maturation process. During diminished chalone production (e.g. after
cell injury and subsequent regeneration), we will get a more or less unrestricted cell proliferation in the tissue with a
delayed maturation process prolonging the chalone depletion. This interaction between the circadian proliferative factor and
the negative feedback factor for regulation of proliferation with its accompanying stimulatory effect on maturation, may represent
a general mechanism in the regulation of cell proliferation in any tissue. Since in at least some organs virtually all cells
entering the S phase do this as a single wave once a day, this mechanism may be enough to explain the regulation of cell proliferation
during both normal and regenerative conditions. 相似文献
209.
210.
Quantification of Toxic Cyanobacteria in Water by Use of Competitive PCR Followed by Sequence-Specific Labeling of Oligonucleotide Probes 总被引:6,自引:1,他引:5
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Knut Rudi Olav M. Skulberg Frank Larsen Kjetill S. Jakobsen 《Applied microbiology》1998,64(7):2639-2643
A complete nucleic-acid-based assay which consists of sample preparation, DNA amplification, and chromogenic detection was developed for quantifying potential toxin-producing cyanobacteria of interest to the public. The sample preparation strategy involves the same solid phase for cell concentration and DNA purification. For the detection step, we used a combination of competitive PCR amplification, sequence-specific labeling of oligonucleotide probes, hybridization of the labeled oligonucleotides to immobilized complements and, finally, chromogenic detection. The complete assay was tested with water containing toxin-producing cyanobacteria belonging to the genus Microcystis. A detection limit of 100 cells/ml and a quantitative range of more than 3 orders of magnitude were obtained. This approach can easily be adapted to a wide range of bacterial species and has the potential for simultaneous detection and quantitation of several different target organisms by a single assay. 相似文献