Evidence for a plasma-membrane-bound nitrate reductase involved in nitrate uptake of Chlorella sorokiniana |
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| Authors: | R. Tischner M. R. Ward R. C. Huffaker |
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| Affiliation: | (1) Pflanzenphysiologisches Institut, Unversität Göttingen, Untere Karspüle 2, D-3400 Göttingen, Federal Republic of Germany;(2) Present address: Department of Genetics, Harvard Medical School, 02114 Boston, MA, USA;(3) Present address: Plant Growth Laboratory, University of California, 95616 Davis, CA, USA |
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| Abstract: | Anti-nitrate-reductase (NR) immunoglobulin-G (IgG) fragments inhibited nitrate uptake into Chlorella cells but had no affect on nitrite 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.Abbreviations EDTA ethylenediaminetetraacetic acid - FAD flavine-adenine dinucleotide - IgG immunoglobulin G - NR nitrate reductase - PM plasma membrane - TX-100 Triton X-100 |
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| Keywords: | Chlorella Nitrate reductase (plasma membrane bound) Nitrate uptake Plasma membrane |
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