title: Latent nitrate reductase activity is associated with the plasma membrane of corn roots.
abstract: 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.
authors.affiliation: Plant Growth Laboratory, University of California, Davis 95616, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Ward
authors.forename: H D
authors.initials: HD
authors.lastname: Grimes
authors.forename: R C
authors.initials: RC
authors.lastname: Huffaker
mesh_terms: 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
chemical_list: D008565:Membrane Proteins; D013501:Surface-Active Agents; D012965:Sodium Chloride; D017830:Octoxynol; D009565:Nitrate Reductases; D050901:Nitrate Reductase; D000251:Adenosine Triphosphatases