Latent nitrate reductase activity is associated with the plasma membrane of corn roots.
Latent nitrate reductase activity (NRA) was detected in corn (Zea mays L., Golden Jubilee) root microsome fractions.  Microsome-associated NRA was stimulated up to 20-fold by Triton X-100 (octylphenoxy polyethoxyethanol) whereas soluble NRA was only increased up to 1.2-fold.  Microsome-associated NRA represented up to 19% of the total root NRA.  Analysis of microsomal fractions by aqueous two-phase partitioning showed that the membrane-associated NRA was localized in the second upper phase (U2).  Analysis with marker enzymes indicated that the U2 fraction was plasma membrane (PM).  The PM-associated NRA was not removed by washing vesicles with up to 1.0 M NACl but was solubilized from the PM with 0.05% Triton X-100.  In contrast, vanadate-sensitive ATPase activity was not solubilized from the PM by treatment with 0.1% Triton X-100.  The results show that a protein capable of reducing nitrate is embedded in the hydrophobic region of the PM of corn roots.
Ward
M R
MR
Plant Growth Laboratory, University of California, Davis 95616, USA.
Grimes
H D
HD
Huffaker
R C
RC
D000251:Adenosine Triphosphatases / Q000032:analysis / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000201:enzymology / Q000648:ultrastructure; D003600:Cytosol / Q000201:enzymology; D008565:Membrane Proteins / Q000032:analysis* / Q000187:drug effects / Q000502:physiology; D008861:Microsomes / Q000201:enzymology; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000032:analysis* / Q000187:drug effects / Q000502:physiology; D017830:Octoxynol / Q000494:pharmacology; D018517:Plant Roots / Q000166:cytology / Q000201:enzymology*; D012965:Sodium Chloride / Q000494:pharmacology; D012995:Solubility; D013501:Surface-Active Agents / Q000494:pharmacology; D003313:Zea mays / Q000201:enzymology* / Q000648:ultrastructure
D008565:Membrane Proteins; D013501:Surface-Active Agents; D012965:Sodium Chloride; D017830:Octoxynol; D009565:Nitrate Reductases; D050901:Nitrate Reductase; D000251:Adenosine Triphosphatases