title: Inhibition of nitrate transport by anti-nitrate reductase IgG fragments and the identification of plasma membrane associated nitrate reductase in roots of barley seedlings.
abstract: Membrane associated nitrate reductase (NR) was detected in plasma membrane (PM) fractions isolated by aqueous two-phase partitioning from barley (Hordeum vulgare L. var CM 72) roots.  The PM associated NR was not removed by washing vesicles with 500 millimolar NaCl and 1 millimolar EDTA and represented up to 4% of the total root NR activity.  PM associated NR was stimulated up to 20-fold by Triton X-100 whereas soluble NR was only increased 1.7-fold.  The latency was a function of the solubilization of NR from the membrane.  NR, solubilized from the PM fraction by Triton X-100 was inactivated by antiserum to Chlorella sorokiniana NR.  Anti-NR immunoglobulin G fragments purified from the anti-NR serum inhibited NO3- uptake by more than 90% but had no effect on NO2- uptake.  The inhibitory effect was only partially reversible; uptake recovered to 50% of the control after thorough rinsing of roots.  Preimmune serum immunoglobulin G fragments inhibited NO3- uptake 36% but the effect was completely reversible by rinsing.  Intact NR antiserum had no effect on NO3- uptake.  The results present the possibility that NO3- uptake and NO3- reduction in the PM of barley roots may be related.
authors.affiliation: Plant Growth Laboratory, University of California, Davis 95616.
authors.forename: M R
authors.initials: MR
authors.lastname: Ward
authors.forename: R
authors.initials: R
authors.lastname: Tischner
authors.forename: R C
authors.initials: RC
authors.lastname: Huffaker
mesh_terms: D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D002708:Chlorella / Q000276:immunology; D001467:Hordeum / Q000201:enzymology / Q000378:metabolism*; D007106:Immune Sera / Q000276:immunology / Q000494:pharmacology; D007074:Immunoglobulin G / Q000276:immunology / Q000494:pharmacology*; D009565:Nitrate Reductases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism / Q000493:pharmacokinetics*; D018517:Plant Roots / Q000201:enzymology* / Q000378:metabolism
chemical_list: D007106:Immune Sera; D007074:Immunoglobulin G; D009566:Nitrates; D009565:Nitrate Reductases