title: Evidence for a plasma-membrane-bound nitrate reductase involved in nitrate uptake of Chlorella sorokiniana.
abstract: Anti-nitrate-reductase (NR) immunoglobulin-G (IgG) fragments inhibited nitrate uptake into Chlorella cells but had no affect on nitrate uptake.  Intact anti-NR serum and preimmune IgG fragments had no affect on nitrate uptake.  Membrane-associated NR was detected in plasma-membrane (PM) fractions isolated by aqueous two-phase partitioning.  The PM-associated NR was not removed by sonicating PM vesicles in 500 mM NaCl and 1 mM ethylenediaminetetraacetic acid and represented up to 0.8% of the total Chlorella NR activity.  The PM NR was solubilized by Triton X-100 and inactivated by Chlorella NR antiserum.  Plasma-membrane NR was present in ammonium-grown Chlorella cells that completely lacked soluble NR activity.  The subunit sizes of the PM and soluble NRs were 60 and 95 kDa, respectively, as determined by sodium-dodecyl-sulfate electrophoresis and western blotting.
authors.affiliation: Pharmaphysiologisches Institut, Universität Göttingen, Federal Republic of Germany.
authors.forename: R
authors.initials: R
authors.lastname: Tischner
authors.forename: M R
authors.initials: MR
authors.lastname: Ward
authors.forename: R C
authors.initials: RC
authors.lastname: Huffaker
mesh_terms: D001692:Biological Transport; D002462:Cell Membrane / Q000201:enzymology; D002708:Chlorella / Q000166:cytology / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D003600:Cytosol / Q000201:enzymology; D007106:Immune Sera / Q000276:immunology / Q000494:pharmacology; D007074:Immunoglobulin G / Q000494:pharmacology; D009565:Nitrate Reductases / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000502:physiology*; D009566:Nitrates / Q000493:pharmacokinetics*; D010084:Oxidation-Reduction; D012995:Solubility
chemical_list: D007106:Immune Sera; D007074:Immunoglobulin G; D009566:Nitrates; D009565:Nitrate Reductases