Characterization of plasma membrane bound cation-stimulated ATPase isolated from the roots of Cucumis sativus

1988 ◽  
Vol 66 (7) ◽  
pp. 1470-1473 ◽  
Author(s):  
Abdul Razaque Memon
Keyword(s):  
Plasma Membrane ◽  
Cucumis Sativus ◽  
Direct Interaction ◽  
Monovalent Cation ◽  
Phase System ◽  
Plasma Membrane Atpase ◽  
Cucumis Sativus L ◽  
Membrane Bound ◽  
Cucumber Roots

A membrane fraction enriched with Mg2+- or Mn2+-dependent, monovalent cation stimulated ATPase was isolated from cucumber roots (Cucumis sativus L.) by an aqueous two-polymer phase system of Dextran T500 (6.5%, w/w) and polyethylene glycol (PEG) 3350 (6.5%, w/w) at pH 7.8. The ATPase activity associated with the upper PEG-rich fraction (plasma membrane) was characterized. The optimum pH for the activation by Mg2+ and Mn2+ was in the range 5.8–6.0. The activity was substrate specific for ATP. Kinetics with Mg2+ or Mn2+ followed a simple Michaelis–Menten relationship. The apparent Km for Mg2+ activation (0.60 mM) of the ATPase was about twice that of the apparent Km for Mn2+ (0.38 mM). ATPase was stimulated by monovalent cations and showed an order of cation preference of [Formula: see text]. Calcium inhibited the plasma membrane ATPase, apparently by a direct interaction with ATPase rather than by disrupting the MgATP2− complex.

scholarly journals Comparative studies on the soluble and plasma membrane associated nitrate reductase from Cucumis sativus L.

2014 ◽  
Vol 63 (3-4) ◽  
pp. 309-314 ◽  
Author(s):  
Grażyna Kłobus ◽  
Jolanta Marciniak ◽  
Józef Buczek
Keyword(s):  
Plasma Membrane ◽  
Nitrate Reductase ◽  
Plasma Membranes ◽  
Polyclonal Antiserum ◽  
Soluble Form ◽  
Phase System ◽  
Two Phase ◽  
Cucumis Sativus L ◽  
Cucumber Roots ◽  
Biochemical Comparison

The biochemical comparison between two forms of nitrate reductase from cucumber roots: the soluble enzyme and the plasma membrane-associated one was made. Soluble nitrate reductase was purified on the blue-Sepharose 4B. The nitrate reductase bound with plasma membranes was isolated from cucumber roots by partition of microsomes in the 6.5% dextran-PEG two phase system. The molecular weight of native enzyme estimated with HPLC was 240 kDa and 114 kDa for the soluble and membrane bounded enzyme, respectively. Temperature induced phase separation in Triton X-114 indicated a huge difference in hydrophobicity of the plasma membrane associated nitrate reductase and soluble form of enzyme. Small differences were observed in partial activities of plasma membrane nitrate reductase and soluble nitrate reductase. Also experiments with polyclonal antiserum raised against the native nitrate reductase showed some differences in the immunological properties of both forms of the nitrate reductase. The above results indicated that in cucumber roots two different forms of the nitrate reductase are present.

scholarly journals Secretory vesicles externalize the major plasma membrane ATPase in yeast.

1988 ◽  
Vol 106 (3) ◽  
pp. 641-648 ◽  
Author(s):  
C L Holcomb ◽  
W J Hansen ◽  
T Etcheverry ◽  
R Schekman
Keyword(s):  
Plasma Membrane ◽  
Secretory Pathway ◽  
Biochemical Characterization ◽  
Plasma Membrane Atpase ◽  
Membrane Assembly ◽  
Yeast Cell Surface ◽  
Membrane Atpase ◽  
Constitutive Secretion ◽  
Secretory Enzyme

Yeast cell surface growth is accomplished by constitutive secretion and plasma membrane assembly, culminating in the fusion of vesicles with the bud membrane. Coordination of secretion and membrane assembly has been investigated by examining the biogenesis of plasma membrane ATPase (PM ATPase) in secretion-defective (sec) strains of Saccharomyces cerevisiae. PM ATPase is synthesized as a approximately 106-kD polypeptide that is not detectably modified by asparagine-linked glycosylation or proteolysis during transit to the plasma membrane. Export of the PM ATPase requires the secretory pathway. In sec1, a mutant defective in the last step of secretion, large amounts of Golgi-derived vesicles are accumulated. Biochemical characterization of this organelle has demonstrated that PM ATPase and the secretory enzyme, acid phosphatase, are transported in a single vesicle species.

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