Protein displacement by DExH/D "RNA helicases" without duplex unwinding     

Fairman ME  Maroney PA  Wang W  Bowers HA  Gollnick P  Nilsen TW  Jankowsky E 《Science (New York, N.Y.)》2004,304(5671):730-734

Members of the DExH/D superfamily of nucleic acid-activated nucleotide triphosphatases are essential for virtually all aspects of RNA metabolism, including pre-messenger RNA splicing, RNA interference, translation, and nucleocytoplasmic trafficking. Physiological substrates for these enzymes are thought to be regions of double-stranded RNA, because several DExH/D proteins catalyze strand separation in vitro. These "RNA helicases" can also disrupt RNA-protein interactions, but it is unclear whether this activity is coupled to duplex unwinding. Here we demonstrate that two unrelated DExH/D proteins catalyze protein displacement independently of duplex unwinding. Therefore, the essential functions of DExH/D proteins are not confined to RNA duplexes but can be exerted on a wide range of ribonucleoprotein substrates.  相似文献   

The effects of enriched carbon dioxide atmospheres on plant--insect herbivore interactions     

Fajer ED  Bowers MD  Bazzaz FA 《Science (New York, N.Y.)》1989,243(4895):1198-1200

Little is known about the effects of enriched CO(2) atmospheres, which may exist in the next century, on natural plant-insect herbivore interactions. Larvae of a specialist insect herbivore, Junonia coenia (Lepidoptera: Nymphalidae), were reared on one of its host plants, Plantago lanceolata (Plantaginaceae), grown in either current low (350 parts per million) or high (700 ppm) CO(2) environments. Those larvae raised on high-CO(2) foliage grew more slowly and experienced greater mortality, especially in early instars, than those raised on low-CO(2) foliage. Poor larval performance on high-CO(2) foliage was probably due to the reduced foliar water and nitrogen concentrations of those plants and not to changes in the concentration of the defensive compounds, iridoid glycosides. Adult pupal weight and female fecundity were not affected by the CO(2) environment of the host plant. These results indicate that interactions between plants and herbivorous insects will be modified under the predicted CO(2) conditions of the 21st century.  相似文献   

Juvenile hormone: activity of natural and synthetic synergists     

W S Bowers 《Science (New York, N.Y.)》1968,161(844):895-897

A group of nonsesquiterpenoid compounds currently used commercially as insecticide synergists possesses a high order of juvenile hormone activity and species specificity.  相似文献   

Mechanism of Na+/H+ antiporting     

Arkin IT  Xu H  Jensen MØ  Arbely E  Bennett ER  Bowers KJ  Chow E  Dror RO  Eastwood MP  Flitman-Tene R  Gregersen BA  Klepeis JL  Kolossváry I  Shan Y  Shaw DE 《Science (New York, N.Y.)》2007,317(5839):799-803

Na+/H+ antiporters are central to cellular salt and pH homeostasis. The structure of Escherichia coli NhaA was recently determined, but its mechanisms of transport and pH regulation remain elusive. We performed molecular dynamics simulations of NhaA that, with existing experimental data, enabled us to propose an atomically detailed model of antiporter function. Three conserved aspartates are key to our proposed mechanism: Asp164 (D164) is the Na+-binding site, D163 controls the alternating accessibility of this binding site to the cytoplasm or periplasm, and D133 is crucial for pH regulation. Consistent with experimental stoichiometry, two protons are required to transport a single Na+ ion: D163 protonates to reveal the Na+-binding site to the periplasm, and subsequent protonation of D164 releases Na+. Additional mutagenesis experiments further validated the model.  相似文献   

Natural and synthetic allatotoxins: suicide substrates for juvenile hormone biosynthesis     

Bowers WS  Evans PH  Marsella PA  Soderlund DM  Bettarini F 《Science (New York, N.Y.)》1982,217(4560):647-648

Cytotoxic agents with antijuvenile hormone activity in insects have been discovered. Their mechanism of action may involve an oxidative bioactivation into a reactive quinone methide.  相似文献   

Subnanometer-Diameter Wires Isolated in a Polymer Matrix by Fast Polymerization     

JH Golden  FJ DiSalvo  JMJ Frechet  J Silcox  M Thomas  J Elman 《Science (New York, N.Y.)》1996,273(5276):782-784

The preparation and analysis of inorganic-organic polymer nanocomposites consisting of inorganic nanowires and multiwire "cables" in a random-coil organic polymer host is reported. Dissolution of inorganic (LiMo3Se3)n wires in a strongly coordinating monomer, vinylene carbonate, and the use of a rapid polymerization in the presence of a cross-linking agent produce nanocomposites without phase separation. Polymerization of dilute solutions yields a material containing mostly (Mo3Se3(-))n mono- and biwires, 6 to 20 angstroms in diameter and 50 to 100 nanometers long. Polymerization of more concentrated liquid crystalline solutions yields a nanocomposite containing oriented multiwire cables, 20 to 40 angstroms in diameter and up to 1500 nanometers long, that display optical anisotropy and electrical conductivity.  相似文献   

A European insect species     

Bowers MD 《Science (New York, N.Y.)》1982,218(4568):150

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高油玉米等比例替代普通玉米对生长肥育猪生产性能影响的评定   总被引：1，自引：0，他引：1  

K.A.Bowers  D.C.Kendall  B.T.Richert  罗兰 《江西饲料》2003,(5):25-27

引言高油玉米是普通黄玉米中的一个特殊品种,它的含油量比普通黄玉米高。该玉米较高的含油量提高了生长肥育猪日粮中的能量浓度。高能量浓度的日粮具有进一步改善饲料报酬的潜力,生猪养殖者可从中获得经济效益。本研究旨在评定高油玉米和普通玉米对生长肥育猪生产性能的影响:平均日增重(ADG),平均日采食量(ADFI),饲料报酬(G:F),脂肪和腰肌厚度,胴体重和胴体品质的额外价格补贴,以及瘦肉率。试验期间为1999年2月至5月。1试验设计试验采用4个日粮处理,分别用普通玉米(NC)和高油玉米(HOC)配制,试验为16周(生长阶段8周,育肥阶段8周)。日粮…  相似文献   

Poisoning of cattle attributed to Cucumis melo ssp agrestis (Ulcardo melon)     

TF JUBB  JH CREEPER  RA McKENZIE 《Australian veterinary journal》1995,72(7):274-275

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Microsporidiosis in a peach-faced lovebird (Agapornis roseicollis)     

JH NORTON  HC PRIOR 《Australian veterinary journal》1994,71(1):23-24

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