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91.
Different mechanistic requirements for prokaryotic and eukaryotic chaperonins: a lattice study 总被引:1,自引:0,他引:1
MOTIVATION: The folding of many proteins in vivo and in vitro is assisted by molecular chaperones. A well-characterized molecular chaperone system is the chaperonin GroEL/GroES from Escherichia coli which has a homolog found in the eukaryotic cytosol called CCT. All chaperonins have a ring structure with a cavity in which the substrate protein folds. An interesting difference between prokaryotic and eukaryotic chaperonins is in the nature of the ATP-mediated conformational changes that their ring structures undergo during their reaction cycle. Prokaryotic chaperonins are known to exhibit a highly cooperative concerted change of their cavity surface while in eukaryotic chaperonins the change is sequential. Approximately 70% of proteins in eukaryotic cells are multi-domain whereas in prokaryotes single-domain proteins are more common. Thus, it was suggested that the different modes of action of prokaryotic and eukaryotic chaperonins can be explained by the need of eukaryotic chaperonins to facilitate folding of multi-domain proteins. RESULTS: Using a 2D square lattice model, we generated two large populations of single-domain and double-domain substrate proteins. Chaperonins were modeled as static structures with a cavity wall with which the substrate protein interacts. We simulated both concerted and sequential changes of the cavity surfaces and demonstrated that folding of single-domain proteins benefits from concerted but not sequential changes whereas double-domain proteins benefit also from sequential changes. Thus, our results support the suggestion that the different modes of allosteric switching of prokaryotic and eukaryotic chaperonin rings have functional implications as it enables eukaryotic chaperonins to better assist multi-domain protein folding. 相似文献
92.
Kathrin I Odörfer Nina J Unger Karin Weber Eric P Sandgren Reinhold G Erben 《BMC biotechnology》2007,7(1):30
Background
Immune-mediated rejection of labeled cells is a general problem in transplantation studies using cells labeled with any immunogenic marker, and also in gene therapy protocols. The aim of this study was to establish a syngeneic model for long-term histological cell tracking in the absence of immune-mediated rejection of labeled cells in immunocompetent animals. We used inbred transgenic Fischer 344 rats expressing human placental alkaline phosphatase (hPLAP) under the control of the ubiquitous R26 promoter for this study. hPLAP is an excellent marker enzyme, providing superb histological detection quality in paraffin and plastic sections. 相似文献93.
Global trade will accelerate plant invasions in emerging economies under climate change 总被引:1,自引:0,他引:1 下载免费PDF全文
Hanno Seebens Franz Essl Wayne Dawson Nicol Fuentes Dietmar Moser Jan Pergl Petr Pyšek Mark van Kleunen Ewald Weber Marten Winter Bernd Blasius 《Global Change Biology》2015,21(11):4128-4140
Trade plays a key role in the spread of alien species and has arguably contributed to the recent enormous acceleration of biological invasions, thus homogenizing biotas worldwide. Combining data on 60‐year trends of bilateral trade, as well as on biodiversity and climate, we modeled the global spread of plant species among 147 countries. The model results were compared with a recently compiled unique global data set on numbers of naturalized alien vascular plant species representing the most comprehensive collection of naturalized plant distributions currently available. The model identifies major source regions, introduction routes, and hot spots of plant invasions that agree well with observed naturalized plant numbers. In contrast to common knowledge, we show that the ‘imperialist dogma,’ stating that Europe has been a net exporter of naturalized plants since colonial times, does not hold for the past 60 years, when more naturalized plants were being imported to than exported from Europe. Our results highlight that the current distribution of naturalized plants is best predicted by socioeconomic activities 20 years ago. We took advantage of the observed time lag and used trade developments until recent times to predict naturalized plant trajectories for the next two decades. This shows that particularly strong increases in naturalized plant numbers are expected in the next 20 years for emerging economies in megadiverse regions. The interaction with predicted future climate change will increase invasions in northern temperate countries and reduce them in tropical and (sub)tropical regions, yet not by enough to cancel out the trade‐related increase. 相似文献
94.
Siton O Ideses Y Albeck S Unger T Bershadsky AD Gov NS Bernheim-Groswasser A 《Current biology : CB》2011,21(24):2092-2097
Cortactin is involved in invadopodia and podosome formation [1], pathogens and endosome motility [2], and persistent lamellipodia protrusion [
[3]
and
[4]
]; its overexpression enhances cellular motility and metastatic activity [
[5]
,
[6]
,
[7]
and
[8]
]. Several mechanisms have been proposed to explain cortactin's role in Arp2/3-driven actin polymerization [
[9]
and
[10]
], yet its direct role in cell movement remains unclear. We use a biomimetic system to study the mechanism of cortactin-mediated regulation of actin-driven motility [11]. We tested the role of different cortactin variants that interact with Arp2/3 complex and actin filaments distinctively. We show that wild-type cortactin significantly enhances the bead velocity at low concentrations. Single filament experiments show that cortactin has no significant effect on actin polymerization and branch stability, whereas it strongly affects the branching rate driven by Wiskott-Aldrich syndrome protein (WASP)-VCA fragment and Arp2/3 complex. These results lead us to propose that cortactin plays a critical role in translating actin polymerization at a bead surface into motion, by releasing WASP-VCA from the new branching site. This enhanced release has two major effects: it increases the turnover rate of branching per WASP molecule, and it decreases the friction-like force caused by the binding of the moving surface with respect to the growing actin network. 相似文献
95.
Most emerging diseases of humans originate in animals, and zoonotic emerging infectious diseases (EIDs) threaten human, animal,
and environment health. We report on a scoping study to assess actors, linkages, priorities, and needs related to management
of these diseases from the perspective of key stakeholders in three countries in Southeast Asia. A comprehensive interview
guide was developed and in-depth interviews completed with 21 key stakeholders in Vietnam, Lao People’s Democratic Republic,
and Cambodia. We found numerous relevant actors with a predominance of public sector and medical disciplines. More capacity
weaknesses than strengths were reported, with risk analysis and research skills most lacking. Social network analysis of information
flows showed policy-makers were regarded as mainly information recipients, research institutes as more information providers,
and universities as both. Veterinary and livestock disciplines emerged as an important “boundary-spanning” organization with
linkages to both human health and rural development. Avian influenza was regarded as the most important zoonotic EID, perhaps
reflecting the priority-setting influence of actors outside the region. Stakeholders reported a high awareness of the ecological
and socioeconomic drivers of disease emergence and a demand for disease prioritization, epidemiological skills, and economic
and qualitative studies. Evaluated from an ecohealth perspective, human health is weakly integrated with socioeconomics, linkages
to policy are stronger than to communities, participation occurs mainly at lower levels, and equity considerations are not
fully considered. However, stakeholders have awareness of ecological and social determinants of health, and a basis exists
on which transdisciplinarity, equity, and participation can be strengthened. 相似文献
96.
Karanicolas J Corn JE Chen I Joachimiak LA Dym O Peck SH Albeck S Unger T Hu W Liu G Delbecq S Montelione GT Spiegel CP Liu DR Baker D 《Molecular cell》2011,42(2):250-260
The de novo design of protein-protein interfaces is a stringent test of our understanding of the principles underlying protein-protein interactions and would enable unique approaches to biological and medical challenges. Here we describe a motif-based method to computationally design protein-protein complexes with native-like interface composition and interaction density. Using this method we designed a pair of proteins, Prb and Pdar, that heterodimerize with a Kd of 130 nM, 1000-fold tighter than any previously designed de novo protein-protein complex. Directed evolution identified two point mutations that improve affinity to 180 pM. Crystal structures of an affinity-matured complex reveal binding is entirely through the designed interface residues. Surprisingly, in the in vitro evolved complex one of the partners is rotated 180° relative to the original design model, yet still maintains the central computationally designed hotspot interaction and preserves the character of many peripheral interactions. This work demonstrates that high-affinity protein interfaces can be created by designing complementary interaction surfaces on two noninteracting partners and underscores remaining challenges. 相似文献
97.
The large, comprehensive vegetation database of Mecklenburg-Vorpommern/NE Germany with 51,328 relevés allowed us to study
an entire regional flora of 133 non-native plants (NNP, immigration after 1492 AD) with regard to their preferences to all
kinds of habitats and along different ecological gradients. For each relevé, we computed average Ellenberg indicator values
(EIV) for temperature, light, moisture, reaction, nutrients and salt as well as plant strategy type weights. We partitioned
the dataset into relevés with and without occurrences of NNP and compared them with respect to the relative frequencies of
EIVs and strategy type weights. We identified deviations from random differences by testing against permuted indicator values.
To account for bias in EIV between community types, NNP preferences were differentiated for 34 phytosociological classes.
We tested significance of preferences for the group of NNP as a whole, as well as for single NNP species within the entire
dataset, as well as differentiated by phytosociological classes and formations. NNP as a group prefer communities with high
EIVs for temperature and nutrients and low EIVs for moisture. They avoid communities with low EIV for reaction and high EIV
for salt. NNP prefer communities with high proportions of ruderal and low proportion of stress strategists. The differentiation
by phytosociological classes reinforces the general trends for temperature, nutrients, moisture, R and S strategy types. Nevertheless,
preferences of single species reveal that NNP are not a congruent group but show individualistic ecological preferences. 相似文献
98.
Citrate is an intermediate in catabolic as well as biosynthetic pathways and is an important regulatory molecule in the control of glycolysis and lipid metabolism. Mass spectrometric and NMR based metabolomics allow measuring citrate concentrations, but only with limited spatial and temporal resolution. Methods are so far lacking to monitor citrate levels in real-time in-vivo. Here, we present a series of genetically encoded citrate sensors based on Förster resonance energy transfer (FRET). We screened databases for citrate-binding proteins and tested three candidates in vitro. The citrate binding domain of the Klebsiella pneumoniae histidine sensor kinase CitA, inserted between the FRET pair Venus/CFP, yielded a sensor highly specific for citrate. We optimized the peptide linkers to achieve maximal FRET change upon citrate binding. By modifying residues in the citrate binding pocket, we were able to construct seven sensors with different affinities spanning a concentration range of three orders of magnitude without losing specificity. In a first in vivo application we show that E. coli maintains the capacity to take up glucose or acetate within seconds even after long-term starvation. 相似文献
99.
K. Unger 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1959,29(7):289-293
Ohne ZusammenfassungMit 8 AbbildungenQuedlinburger Beiträge zur Züchtungsforschung Nr. 43. 相似文献
100.