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  • 1
    Publication Date: 2007-08-04
    Description: BtuCD is an adenosine triphosphate-binding cassette (ABC) transporter that translocates vitamin B12 from the periplasmic binding protein BtuF into the cytoplasm of Escherichia coli. The 2.6 angstrom crystal structure of a complex BtuCD-F reveals substantial conformational changes as compared with the previously reported structures of BtuCD and BtuF. The lobes of BtuF are spread apart, and B12 is displaced from the binding pocket. The transmembrane BtuC subunits reveal two distinct conformations, and the translocation pathway is closed to both sides of the membrane. Electron paramagnetic resonance spectra of spin-labeled cysteine mutants reconstituted in proteoliposomes are consistent with the conformation of BtuCD-F that was observed in the crystal structure. A comparison with BtuCD and the homologous HI1470/71 protein suggests that the structure of BtuCD-F may reflect a posttranslocation intermediate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hvorup, Rikki N -- Goetz, Birke A -- Niederer, Martina -- Hollenstein, Kaspar -- Perozo, Eduardo -- Locher, Kaspar P -- New York, N.Y. -- Science. 2007 Sep 7;317(5843):1387-90. Epub 2007 Aug 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Molecular Biology and Biophysics, ETH Zurich, HPK D14.3, 8093 Zurich, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17673622" target="_blank"〉PubMed〈/a〉
    Keywords: ATP-Binding Cassette Transporters/*chemistry ; Amino Acid Sequence ; Crystallography, X-Ray ; Electron Spin Resonance Spectroscopy ; Escherichia coli ; Escherichia coli Proteins/*chemistry ; Models, Molecular ; Molecular Sequence Data ; Periplasmic Binding Proteins/*chemistry ; Protein Binding ; Protein Conformation ; Recombinant Fusion Proteins/chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    ISSN: 1432-2285
    Keywords: Picea abies ; Ectomycorrhizae ; Physiological ecology ; Forest decline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The mycorrhizal activity of spruce in a mixed-wood forest was monitored over 1 year by measuring biochemical characters in fine roots of six canopy trees and of a regrowth stand. The concentration of adenosine 5′-triphosphate (ATP), a measure of living biomass, showed two peaks per year, one at bud break and one after main shoot growth. The concentration of storage polysaccharides in mycorrhizae showed the same cycles even more pronouncedly. It is proposed that these changes reflect growth and senescence of mycorrhizae and that the timing of the cycles is controlled by translocation of assimilates from the shoot. Differences between mycorrhizae collected from canopy trees and the regrowth stand were small and not significant. Characters known to be related to fungal activity of the mycorrhizal symbiosis (concentration of trehalose, glucose uptake, respiration) also varied little among the six canopy trees. Large differences among fine-root samples from different canopy trees, however, were detected in the concentrations of ATP and storage polysaccharides, measures which seemed to be physiologically integrated within trees. If low concentrations in roots precede losses of foliage from trees, these two symptoms could be used as early indicators of growth decline in individual spruce trees.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2285
    Keywords: Picea abies ; Ectomycorrhizae ; Physiological ecology ; Forest decline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The mycorrhizal activity of spruce in a mixed-wood forest was monitored over 1 year by measuring biochemical characters in fine roots of six canopy trees and of a regrowth stand. The concentration of adenosine 5′-triphosphate (ATP), a measure of living biomass, showed two peaks per year, one at bud break and one after main shoot growth. The concentration of storage polysaccharides in mycorrhizae showed the same cycles even more pronouncedly. It is proposed that these changes reflect growth and senescence of mycorrhizae and that the timing of the cycles is controlled by translocation of assimilates from the shoot. Differences between mycorrhizae collected from canopy trees and the regrowth stand were small and not significant. Characters known to be related to fungal activity of the mycorrhizal symbiosis (concentration of trehalose, glucose uptake, respiration) also varied little among the six canopy trees. Large differences among fine-root samples from different canopy trees, however, were detected in the concentrations of ATP and storage polysaccharides, measures which seemed to be physiologically integrated within trees. If low concentrations in roots precede losses of foliage from trees, these two symptoms could be used as early indicators of growth decline in individual spruce trees.
    Type of Medium: Electronic Resource
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