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  • 1
    Electronic Resource
    Electronic Resource
    Physical properties of the cell wall of photoautotrophic suspension cells fromChenopodium rubrum L. (1988)
    Springer
    Planta 174 (1988), S. 333-339 
    Details
    ISSN: 1432-2048
    Keywords: Cell culture (photoautotrophic) ; Cell wall porosity ; Charge density ; Chenopodium ; Donnan potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoautotrophic suspension cells ofChenopodium rubrum were used to determine Donnan potential, charge density and pore-radius distribution in the cell wall. Experiments were done either with turgescent cells or with isolated cell walls. Titration of a cell-wall-generated 9-aminoacridine fluorescence quench with salts of mono- and divalent cations was used to determine Donnan potential and charge density. The experiments and theory were adapted from measurements of membrane surface charges. A tenfold increase in ionic strength, which decreases the repellant forces between charges of the same sign, led to an approximately threefold increase in the measured charge density, thus resulting in a much smaller decrease of the Donnan potential than would be expected if the charge density remained fixed. This decreased influence of ionic strength on the Donnan potential, resulting from the elasticity of the cell wall, was also measurable but less pronounced when the wall of intact cells was stretched by turgor. The porosity of the cell wall was determined by longterm uptake of polyethylene glycols of different molecular weights, and by gel filtration of polyethylene glycols and dextrans as well as mono- and disaccharides using intact suspension cells as matrix. Both methods gave a mean pore diameter of about 4.5 nm and a maximum pore size of 5.5 nm. The resulting pores-size distribution was slightly broader with the latter method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959518
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  • 2
    Electronic Resource
    Electronic Resource
    Sugar nucleotides dissipate ATP-generated transmembrane pH gradient in Golgi vesicles from suspension-cell protoplasts ofChenopodium rubrum L. (1988)
    Springer
    Planta 174 (1988), S. 349-357 
    Details
    ISSN: 1432-2048
    Keywords: Chenopodium ; Golgi vesicle ; Proton ATPase ; Protoplast ; Sugar nucleotide ; Suspension cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A microsomal vesicle fraction (GV) markedly enriched by the Golgi marker enzyme latent inosine diphosphatase (IDPase) has been isolated from photoautotrophic suspension-cell protoplasts ofChenopodium rubrum L. Addition of ATP creates a substantial pH gradient across the GV membrane as measured by accumulation of acridine orange. The GV showed a density of 1.14 g·cm-3 by equilibrium density centrifugation on sucrose gradients. Coincidence of acridine-orange accumulation and IDPase activity was confirmed on Percoll gradients. Formation of the pH gradient half-saturates at 0.3 mM MgATP, peaks at pH 7, and is competitively inhibited by ADP (k i≤0.1 mM), but not by Pi; it is hardly inhibited by orthovanadate, quickly dissipated by monensink 2=18 nM), nigericin (k 1/2=25 nM), and sluggishly by N-ethylmaleimide (k 1/2≈35 μM). Inhibition by KNO3 (k 1/2≈6.7 mM) is incomplete (60%). Uridine 5′-diphosphate (UDP)-glucose, UDP-galactose, but not UDP-mannose and the pertinent sugars, dissipate the ATP-generated pH gradient (k 1/2≈10–20 mM UDP-glucose; optimum pH at 7.8). This UDP-glucose activity is accompanied by release of Pi, but not of glucose or sucrose. UDP-glucoseinduced Pi release from the GV saturates (k 1/2=1 mM UDP-glucose; optimum pH at 7) and is completely inhibited by the anion-channel blocker 4,4′-diisothiocyano-2,2′-stilbene disulfonic acid (DIDS;k 1/2=140 μM). The GV incorporates UDP-[U-14C]glucose into an acid-labile, alkaline-stable macromolecular compound; this process is like-wise inhibited by DIDS. We propose a model including, inter alia, a UDP-glucose/uridine-5′-monophosphate translocator and a phosphate-permeable anion channel to operate in Golgi vesicles ofChenopodium rubrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959520
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