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  • Vicia (guard cells)  (2)
  • Actin isoforms  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Planta 161 (1984), S. 27-31 
    ISSN: 1432-2048
    Keywords: Guard cell vacuoles ; Malic acid ; Vacuole (swelling process) ; Vicia (guard cells)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method for the preparation of vacuoles from guard cells ofVicia faba L. is described. Vacuoles were released from guard-cell protoplasts by osmotic shock and purified on a Ficoll gradient. Contamination of the vacuoles was examined by assaying marker enzymes, such as fumarase, glucose-6-phosphate dehydrogenase, phosphofructokinase, acid phosphatase and mannosidase. Potassium ions in the incubation medium caused increases in the volume of the vacuoles by a factor of about 2.6, while the malate level remained unchanged. In contrast, malate synthesis was stimulated during the swelling phase when complete guard-cell protoplasts were exposed to K+. The possible role of K+ as an efficient osmotic effector is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Guard cell protoplast ; Malate sensitivity ; Phosphoenolpyruvate carboxylase ; Protoplast (guard cell) ; Vicia (guard cells)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Properties of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) obtained from isolated guard-cell protoplasts of Vicia faba L. were determined following rapidly desalting of the extract on a Sephadex G 25 column. The activity of PEP carboxylase was measured as a function of PEP and malate concentration, pH and K+ concentration within 2–3 min after homogenization of the guard-cell protoplasts. The activity of this enzyme was stimulated by PEP concentrations of 0.1 to 0.75 mM and by K+ ions (12 mM), but inhibited by PEP concentrations above 1 mM and by malate. Changes in the Km(PEP) and Vmax values with increasing malate concentrations (2.5 and 5 mM) indicate that the malate level, varying in relation to the physiological state of guard cells, plays an important role in regulating the properties of phosphoenolpyruvate carboxylase.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 191 (1996), S. 158-163 
    ISSN: 1615-6102
    Keywords: Actin isoforms ; Tissue distribution ; Intracellular compartmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two dimensional gel electrophoresis of total cell protein extracts from not expanded, and primary leaves, petioles, and roots ofVicia faba resulted in four actin isoforms at 43 kDa with pI values from 5.9 to 6.05. In contrast to root extracts, in all leaf extracts an additional immunoreactive polypeptide with a molecular mass of 51 kDa and pI 5.75 was detected. This polypeptide was present in high amounts in protein extracts of purified chloroplasts, whereas no actin isoform at 43 kDa could be demonstrated. Compared to the tissue extracts, two actin isoforms at 43 kDa with pI values of 5.9 and 6.0 were enriched, when purified plasma membranes and the membranous fraction of vacuoles were analysed. In contrast, the soluble protein fraction of the plasma membrane preparation contained only two isoactins with pI values of 5.95 and 6.05 and a molecular mass of 43 kDa. These results indicate, that the four actin isoforms at 43 kDa detected in all examined tissues ofV. faba fulfill different functions at specific intracellular compartments, for example, the anchorage of actin microfilaments to membranes.
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