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  • 1
    Electronic Resource
    Electronic Resource
    The Golgi apparatus mediates the transport of phytohemagglutinin to the protein bodies in bean cotyledons (1983)
    Springer
    Planta 158 (1983), S. 140-151 
    Details
    ISSN: 1432-2048
    Keywords: Endoplasmic reticulum ; Golgi apparatus ; Lectin ; Phaseolus (transport of protein) ; Phytohemagglutinin ; Protein body ; Storage protein ; Transport (protein)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When developing cotyledons of Phaseolus vulgaris L. were labeled with [3H]fucose, fucose-labeled phytohemagglutinin (PHA) was found in organelles with average densities of 1.13 g cm-3 and 1.22 g cm-3. The position of these organelles on isopycnic sucrose gradients was independent of the presence of MgCl2 and ethylenediaminetetraacetate in the media, indicating that the fucose-labeled PHA was not associated with the rough endoplasmic reticulum (ER). The organelles with a density of 1.13 g cm-3 were identified as membranes of the Golgi apparatus on the basis of the similarity of their sedimentation properties and those of the Golgi marker enzyme, inosine diphosphatase, in both isopycnic and rate-zonal sucrose gradients. The organelles with a density of 1.22 g cm-3 were identified as small (0.1–0.4 μm), electron-dense vesicles with a protein content similar to that of the protein bodies. Pulsechase experiments with [3H]fucose indicated that fucose-labeled PHA first appeared in the Golgi-apparatus-derived membranes and later in the dense vesicles. Fucose-labeled PHA chased out of the Golgi apparatus first, then out of the dense vesicles, and accumulated in the soluble portion of the homogenate which contained the contents of the broken protein bodies. Fucose-labeled PHA chased out of the two types of organelles with a t 1/2 of 20–30 min, a rate three to four times faster than newly synthesized PHA chases out of the bulk of the ER (Chrispeels, M.J., Bollini, R., 1982, Plant Physiol. 70, 1425–1428). This result indicates that the Golgi apparatus is a much smaller compartment than the ER in the storage parenchyma cells. The sodium ionophore, monensin, which interferes with the function of the Golgi apparatus of animal cells, blocks the biosynthesis and—or transport of fucose- and galactose-labeled macromolecules to the cotyledon cell walls. Monensin also blocks the transport of labeled PHA out of the Golgi apparatus and into the protein bodies. These results provide the first biochemical evidence that a specific storage protein which accumulates in seeds is modified in, and passes through, the Golgi apparatus on its way to the protein bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397707
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Correct glycosylation, Golgi-processing, and targeting to protein bodies of the vacuolar protein phytohemagglutinin in transgenic tobacco (1988)
    Springer
    Planta 175 (1988), S. 170-183 
    Details
    ISSN: 1432-2048
    Keywords: Golgi apparatus ; Nicotiana (transgenic) ; Phaseolus (phytohemagglutinin) ; Phytohemagglutinin ; Protein bodies ; Protein targeting ; Transformation (tobacco)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used a heterologous system (transgenic Nicotiana tabacum L.) to investigate the processing, assembly and targeting of phytohemagglutinin (PHA), the lectin of the common bean, Phaseolus vulgaris L. In the bean, this glycoprotein accumulates in the protein bodies of the storage parenchyma cells in the cotyledons, and each polypeptide has a high-mannose glycan attached to Asn12 and a complex glycan on Asn60. The gene for PHA-L, dlec2, with 1200 basepairs (bp) 5′ upstream and 1600 bp 3′ downstream from the coding sequence was introduced into tobacco using Agrobacterium-mediated transformation (T. Voelker et al., 1987, EMBO J. 6, 3571–3577). Examination of thin sections of tobacco seeds by immunocytochemistry with antibodies against PHA showed that PHA-L accumulated in the amorphous matrix of the protein bodies in the embryo and endosperm. This localization was confirmed using a non-aqueous method to isolate the protein bodies from mature tobacco seeds. The biochemical analysis of tobacco PHA indicated that the signal peptide had been correctly removed, and that the polypeptides formed 6.4 S oligomers; tobacco PHA had a high-mannose glycan at Asn12 and a complex glycan at Asn60. The presence of the complex glycan shows that transport to the protein bodies was mediated by the Golgi complex. At seed maturity, a substantial portion of the PHA-L remained associated with the endoplasmic reticulum and the Golgi complex, as indicated by fractionation experiments using aqueous media and the presence of two high-mannose glycans on some of the polypeptides. Taken together, these data show that insertion of the nascent PHA into the endoplasmic reticulum, signal peptide processing, glycosylation, assembly into oligomers, glycan modification in the Golgi, and targeting of the protein occur faithfully in this heterologous system, although transport may not be as efficient as in bean cotyledons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392425
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    Paper (German National Licenses)
    Fulltext
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