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41.
Ping Li Niloofar Nayeri Kamil Grecki Eva Ramos Becares Kaituo Wang Dhani Ram Mahato Magnus Andersson Sameera S. Abeyrathna Karin LindkvistPetersson Gabriele Meloni Julie Winkel Missel Pontus Gourdon 《Protein science : a publication of the Protein Society》2022,31(7)
Copper (Cu) is one of the most abundant trace metals in all organisms, involved in a plethora of cellular processes. Yet elevated concentrations of the element are harmful, and interestingly prokaryotes are more sensitive for environmental Cu stress than humans. Various transport systems are present to maintain intracellular Cu homeostasis, including the prokaryotic plasmid‐encoded multiprotein pco operon, which is generally assigned as a defense mechanism against elevated Cu concentrations. Here we structurally and functionally characterize the outer membrane component of the Pco system, PcoB, recovering a 2.0 Å structure, revealing a classical β‐barrel architecture. Unexpectedly, we identify a large opening on the extracellular side, linked to a considerably electronegative funnel that becomes narrower towards the periplasm, defining an ion‐conducting pathway as also supported by metal binding quantification via inductively coupled plasma mass spectrometry and molecular dynamics (MD) simulations. However, the structure is partially obstructed towards the periplasmic side, and yet flux is permitted in the presence of a Cu gradient as shown by functional characterization in vitro. Complementary in vivo experiments demonstrate that isolated PcoB confers increased sensitivity towards Cu. Aggregated, our findings indicate that PcoB serves to permit Cu import. Thus, it is possible the Pco system physiologically accumulates Cu in the periplasm as a part of an unorthodox defense mechanism against metal stress. These results point to a previously unrecognized principle of maintaining Cu homeostasis and may as such also assist in the understanding and in efforts towards combatting bacterial infections of Pco‐harboring pathogens. 相似文献
42.
2005年4--5月、6--7月、10--11月笔者在浙江省舟山市嵊泗县大洋山岛(中心点坐标30°34′N,122°4′E进行鸟类调相过程中,记录到日本淡脚柳莺(Phylloscopus borealoides)和硫磺(巫鸟)(Emberiza sulphurata),经查阅相关文献后确认为浙江省鸟类新记录.现报道如下: 相似文献
43.
Phosphorus Limitation in Boreal Forests: Effects of Aluminum and Iron Accumulation in the Humus Layer 总被引:1,自引:1,他引:1
Plant growth in boreal forests is generally considered to be predominantly nitrogen (N) limited, but forested groundwater
discharge areas may be exceptions. In this study, we conducted tests to determine whether highly productive forested groundwater
discharge areas generally differ from adjacent groundwater recharge areas in terms of humus chemistry and the availability
of phosphorus (P) and N to plants. We investigated six forested sites, divided into groundwater discharge and adjacent groundwater
recharge areas, in northern Sweden. The humus layers of the forested groundwater discharge areas were clearly distinguished
from the adjacent groundwater recharge areas by having higher acid-digestible calcium (Ca) and/or aluminium (Al) and iron
(Fe) content and higher organic P and N content. Soil solution inorganic N (NH4
+ and NO3
−) and pH were higher in the groundwater discharge areas than in the groundwater recharge areas. The organic P content showed
a positive linear relationship to the Al and Fe content in the humus layer, indicating that organic P is associated with Al
and Fe compounds in the humus. A plant bioassay using humus substrate from one groundwater discharge area and the adjacent
groundwater recharge area found that plants grown in groundwater discharge area humus (with a high P-fixation capacity) increased
their biomass upon P fertilization, whereas no growth response was found for N additions. By contrast, plants grown in humus
from the groundwater recharge area did not respond to added P unless N was added too. This study suggests that groundwater
discharge can affect the nutrient availability of N and P both directly, via increased P fixation due to the redistribution
of Al and Fe, and indirectly, via the inflow of groundwater high in Ca and alkalinity, maintaining a high pH in the humus
layer that favors in situ N turnover processes.
Received 2 March 2001; Accepted 9 November 2001. 相似文献
44.
45.
John J. Ferrie Conor M. Haney Jimin Yoon Buyan Pan Yi-Chih Lin Zahra Fakhraai Elizabeth Rhoades Abhinav Nath E. James Petersson 《Biophysical journal》2018,114(1):53-64
We describe a strategy for experimentally-constraining computational simulations of intrinsically disordered proteins (IDPs), using α-synuclein, an IDP with a central role in Parkinson’s disease pathology, as an example. Previously, data from single-molecule Förster Resonance Energy Transfer (FRET) experiments have been effectively utilized to generate experimentally constrained computational models of IDPs. However, the fluorophores required for single-molecule FRET experiments are not amenable to the study of short-range (<30 Å) interactions. Using ensemble FRET measurements allows one to acquire data from probes with multiple distance ranges, which can be used to constrain Monte Carlo simulations in PyRosetta. To appropriately employ ensemble FRET data as constraints, we optimized the shape and weight of constraining potentials to afford ensembles of structures that are consistent with experimental data. We also used this approach to examine the structure of α-synuclein in the presence of the compacting osmolyte trimethylamine-N-oxide. Despite significant compaction imparted by 2 M trimethylamine-N-oxide, the underlying ensemble of α-synuclein remains largely disordered and capable of aggregation, also in agreement with experimental data. These proof-of-concept experiments demonstrate that our modeling protocol enables one to efficiently generate experimentally constrained models of IDPs that incorporate atomic-scale detail, allowing one to study an IDP under a variety of conditions. 相似文献
46.
Low serum cholesterol concentrations are associated with deaths from cancer. This association was found in a prospective study of middle aged men in Malmö and consideration of possible explanations for the lowering of serum cholesterol prompted an analysis of serum urate in relation to deaths from cancer. A total of 127 of the 7725 participants in the Malmö study had died since screening. A weakly positive but significant correlation between raised serum urate concentration and total mortality was found. This correlation was wholly explained by neoplastic deaths (p less than 0.01), while there were no associations with alcohol related deaths or with deaths from coronary heart disease. When the deaths from cancer were classified as "early" or "late"--that is, occurring less than or more than 2.5 years after the screening--the correlation between raised urate concentrations and cancer mortality was confined to the "early" deaths (p less than 0.001). Further studies are needed to substantiate the relation between raised serum urate concentrations and fatal neoplasia. Nevertheless, these findings weigh against recent suggestions that uric acid has an antioxidant protective effect against cancer. 相似文献
47.
Magnetic interaction between the tyrosyl free radical and the antiferromagnetically coupled iron center in ribonucleotide reductase 总被引:2,自引:0,他引:2
M Sahlin L Petersson A Gr?slund A Ehrenberg B M Sj?berg L Thelander 《Biochemistry》1987,26(17):5541-5548
Ribonucleotide reductases from Escherichia coli and from mammalian cells are heterodimeric enzymes. One of the subunits, in the bacterial enzyme protein B2 and in the mammalian enzyme protein M2, contains iron and a tyrosyl free radical that both are essential for enzyme activity. The iron center in protein B2 is an antiferromagnetically coupled pair of high-spin ferric ions. This study concerns magnetic interaction between the tyrosyl radical and the iron center in the two proteins. Studies of the temperature dependence of electron paramagnetic resonance (EPR) relaxation and line shape reveal significant differences between the free radicals in proteins B2 and M2. The observed temperature-dependent enhanced EPR relaxation and line broadening of the enzyme radicals are furthermore completely different from those of a model UV-induced free radical in tyrosine. The results are discussed in terms of magnetic dipolar as well as exchange interactions between the free radical and the iron center in both proteins. The free radical and the iron center are thus close enough in space to exhibit magnetic interaction. For protein M2 the effects are more pronounced than for protein B2, indicating a stronger magnetic interaction. 相似文献
48.
Lily N. Edwards Andrew E. Sorkin Richard C. Rhodes Katherine H. Petersson 《Zoo biology》2010,29(4):416-431
The purpose of this study was to identify efficient sampling methods for establishing accurate activity budgets for zoo animals. Seven cotton‐top tamarins (Saguinus oedipus) from two zoos were videotaped for multiple 90 min sessions, 3 to 4 days per week for 12 weeks. An activity budget was constructed for each animal using a continuous sampling method to analyze 30 hr of video recording of each animal. These master datasets, reflecting actual behavior, were re‐sampled using interval sampling lengths of 0.25, 0.5, 1, 2, 4, 5, 7, 10, 15 and 20 min, and cluster sampling protocols (periodic sessions of continuous sampling) of 10 min×3, 15 min×2, 20 min×1, 15 min×1 and 10 min×1 (min×repetitions/90 min sample period) to construct additional activity budgets for each animal. The Canberra similarity index was used to determine the statistical relationship between these activity budgets and those based on the master datasets. As interval length increased, there was a consequent decrease in the accuracy of the associated activity budgets as compared with the master dataset. No cluster sampling protocols yielded activity budgets as accurate as the four shortest interval lengths, but all cluster sampling protocols were more accurate than the three longest interval lengths. All the tested protocols varied in ability to accurately portray animal behavior. Overall, interval sampling provided superior behavioral representations at lower observer input. Results from this study will potentially facilitate the standardization of behavior monitoring protocols at zoos. Zoo Biol 29:416–431, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
49.
In the dance fly species Empis borealis (L.), females (1–40) gather to swarm at landmarks (swarm markers, like trees and bushes), and males carrying an insect prey visit these swarms for mating. We noticed earlier that some swarm sites were used for several years and that they appeared to be frequented by a similar number of swarming females in each year, although the numbers of females varied greatly among swarm sites and certain sites attracted more swarming individuals than others. To explore swarm site fidelity in this mating system, in 1993 we monitored the same swarm sites that we studied in 1989, addressing the questions, Would the same swarm sites still attract the same number of females and males after 4 years? and Why do some swarm sites attract more displaying females than others? The number of females swarming at the different markers in 1993 was approximately the same as 4 years earlier. Some of these swarm sites are known to have been used for 18 years. The swarm sites with the largest number of flies had a high sun exposure during the day and were found at coniferous swarm marker trees and in a mixed forest habitat. A swarm site with few females attending and with a low amount of insolation during the day can be predicted to be abandoned as a swarming site soon. Empis borealis swarm sites thus persist over many years and are attended by a similar number of individuals each year. To our knowledge, such site fidelity has not been demonstrated for any swarming insect species earlier. 相似文献
50.