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1.
Robert Blake II Elizabeth A. Shute James Waskovsky Arthur P. Harrison JR. 《Geomicrobiology journal》2013,30(3-4):173-192
Abstract Microorganisms capable of aerobic respiration on ferrous ions are spread throughout eubacterial and archaebacterial phyla. Phylogenetically distinct organisms were shown to express spectrally distinct redox‐active biomolecules during autotrophic growth on soluble iron. A new iron‐oxidizing eubacterium, designated as strain Funis, was investigated. Strain Funis was judged to be different from other known iron‐oxidizing bacteria on the bases of comparative lipid analyses, 16S rRNA sequence analyses, and cytochrome composition studies. When grown autotrophically on ferrous ions, Funis produced conspicuous levels of a novel acid‐stable, acid‐soluble yellow cytochrome with a distinctive absorbance peak at 579 nm in the reduced state. Stopped‐flow spectrophotometric kinetic studies were conducted on respiratory chain components isolated from cell‐free extracts of Thiobacillus ferrooxidans. Experimental results were consistent with a model where the primary oxidant of ferrous ions is a highly aggregated c‐type cytochrome that then reduces the periplasmic rusticyanin. The Fe(II)‐dependent, cytochrome c‐catalyzed reduction of the rusticyanin possessed three kinetic properties in common with corresponding intact cells that respire on iron: the same anion specificity, a similar dependence of the rate on the concentration of ferrous ions, and similar rates at saturating concentrations of ferrous ions 相似文献
2.
KHALIFAH R. A.; LEWIS L. N.; COGGINS C. W. JR.; RADLICK P. C. 《Journal of experimental botany》1965,16(3):511-517
Evidence for the non-indolic nature of the new citrus auxinis presented on the basis of fluorometric properties, thin-layerchromatography, Ehrlich's colour reaction, paper electrophoresis,and the infra-red spectra determinations. Citrus auxin had alower Rf in TLC than IAA, did not give the typical indole reactionwith Ehrlich's reagent, and behaved differently in electrophoresis.The infra-red spectra also provided preliminary informationconcerning chemical structure. The hypothesis that indolic compoundsconstitute the only natural auxins in higher plants should berevised in view of this evidence that a non-indole auxin existsin higher plants. 相似文献
3.
Developmental expression of prion protein gene in brain 总被引:8,自引:0,他引:8
M P McKinley B Hay V R Lingappa I Lieberburg S B Prusiner 《Developmental biology》1987,121(1):105-110
Synthesis of the cellular isoform of the prion protein (PrPC) was found to be regulated during development of the hamster brain. PrP poly A(+) RNA was readily detectable 10 days postpartum; after 20 days of age, no change in its level could be detected through 13 months of age. Low levels of PrP poly A(+) RNA were detectable 1 day after birth. By contrast, myelin basic protein poly A(+) RNA was found at high levels in brain at 30 days of age and thereafter declined steadily. Using monospecific PrP antisera, immunoprecipitable cell-free translation products were detected at low levels 2 days after birth and increased progressively through 10 days of age. How the levels of PrP mRNA participate in brain development and function remains to be established. 相似文献
4.
Evidence for a secretory form of the cellular prion protein 总被引:8,自引:0,他引:8
The biogenesis of hamster brain prion protein (PrP) has been studied by expression of RNA transcribed from a full-length PrP cDNA in Xenopus oocytes and cell-free systems. Earlier studies in the wheat germ cell-free system showed that one form of PrP is a transmembrane protein that spans the bilayer at least twice [Hay, B., Barry, R. A., Lieberburg, I., Prusiner, S. B., & Lingappa, V. R. (1987) Mol. Cell. Biol. 7, 914-920]. We now report that PrP can also exist as a secreted protein. SP6 PrP RNA microinjected into Xenopus oocytes produced two forms of PrP: one that remained in the cell and another that was secreted into the medium. Cell-free translation studies in rabbit reticulocyte lysates supplemented with microsomal membranes gave similar results: while one form of PrP was found as an integral membrane protein spanning the membrane at least twice, another form of PrP was found to be completely translocated to the microsomal membrane vesicle lumen. Both the membrane and secretory forms of PrP appear to be generated from the same pool of nascent chains. The mechanism governing the alternative fates of nascent PrP remains to be elucidated but may have significance for understanding the pathogenesis of scrapie and other prion diseases. 相似文献
5.
Major histocompatibility (B) complex and sex effects on the phytohaemagglutinin wattle response 总被引:2,自引:0,他引:2
The influence of the major histocompatibility (B) complex and sex on the phytohaemagglutinin (PHA) wattle response was studied in 136 segregants (B2/B2, B2/B5 and B5/B5) of a fourth generation cross between inbred lines 6(1) and 15(1). At 6 weeks of age, chickens were injected with 100 micrograms purified PHA-P. Wattle thickness measurements were taken 4, 24, 48, 72 and 96 h after injection. Analysis of variance showed that 4 h after injection, males had a significantly higher response than females but the sex-genotype interaction was also significant. Females had higher responses than males 24 and 48 h after injection as a consequence of more rapid development and earlier resolution of the reaction in males. B2/B2 chickens had significantly lower responses than B5/B5 chickens 72 and 96 h after injection, signifying a faster late resolution phase in the B2/B2 genotype. The developmental and early resolution phases of the PHA wattle response were influenced by sex while the late resolution phase was influenced by B genotype. 相似文献
6.
Multiple topogenic sequences determine the transmembrane orientation of the hepatitis B surface antigen. 总被引:23,自引:1,他引:22 下载免费PDF全文
To investigate the mechanism by which complex membrane proteins achieve their correct transmembrane orientation, we examined in detail the hepatitis B surface antigen for sequences which determine its membrane topology. The results demonstrated the presence of at least two kinds of topogenic elements: an N-terminal uncleaved signal sequence and an internal element containing both signal and stop-transfer function. Fusion of reporter groups to either end of the protein suggested that both termini are translocated across the membrane bilayer. We propose that this topology is generated by the conjoint action of both elements and involves a specifically oriented membrane insertion event mediated by the internal sequence. The functional properties of each element can be instructively compared with those of simpler membrane proteins and may provide insight into the generation of other complex protein topologies. 相似文献
7.
Allometric Root/Shoot Relationships and Predicted Water Uptake for Desert Succulents 总被引:3,自引:0,他引:3
Root morphology, shoot morphology, and water uptake for Agavedeserti and Ferocactus acanthodes of various sizes were studiedusing allometric relationships (y = axb) and a previously developedwater uptake model. Shoot surface area increased with shootvolume with an exponent b of 0.75 for both species. Root lengthand the ground area explored by the roots increased with shootsurface area with b's of 0.72 for A. deserti and 0.92 for F.acanthodes. Various sized individuals had about the same ratioof root length to explored ground area, with higher values occurringfor A. deserti. Predicted water uptake averaged over the exploredground area was approximately constant over a 104-fold rangein shoot surface area, suggesting that shoot size confers nointraspecific competitive advantage for water uptake. For theroot lengths per explored ground area observed in the field,water uptake was predicted to be 85 per cent of maximal; wateruptake could be increased by the production of more rain roots.When differences in shoot volume were accounted for by allometry,small plants had relatively less shoot surface area and relativelymore root length per shoot volume than did large plants, whichmay be important for the water relations of seedling establishment. Agave deserti, Ferocactus acanthodes, allometry, desert succulents, root distribution, root length, seedling growth, seedling establishment, shoot surface area, shoot volume, water uptake 相似文献
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10.
Gibberellic Acid Sensitivity Determines the Length of the Extension Zone in Wheat Leaves 总被引:2,自引:0,他引:2
To test the hypothesis that gibberellic acid (GA) sensitivityaffects the length of the extension zone (LEZ) of leaf No. 1of wheat seedlings, we performed a gene dosage experiment usingRht dwarfing genes that condition GA insensitivity. We utilizednearly isogenic lines, at Rht-dosage levels of 0, 2 and 4 alleles.Anatomical markers (distances between successive stomates) wereused to infer the distribution of growth along the axis of theleaf. Interstomatal distance (ISD) and LEZ were inverse linearfunctions of Rht-dosage. The number of stomates matured perhour was independent of Rht-dosage. The relationship betweenISD and distance along the axis within the extension zone (EZ)was indistinguishable from linear. Rht-dosage did not affectthe slope of the regression of ISD against distance along theEZ. A-REST (AR; ancymidol, a potent GA synthesis inhibitor)reduced LEZ. Wild type was more sensitive to AR than doubledwarf. AR affected growth of leaf No. 1 more than length ofthe coleoptile, regardless of Rht-dosage. AR-dosage affectedcell division, whereas Rht-dosage did not. Extension zone, elongation, gibberellic acid, Rht, wheat, Triticum aesiivum L. 相似文献