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Characterization of the association of nitrate reductase with barley (Hordeum vulgare L.) root membranesThe nature of the association between nitrate reductase (NR) and membranes was examined. Nitrate reductase activity (NRA) associated with the microsomal fraction of barley (Hordeum vulgare L.) roots amounted to 0.6 to 0.8% of soluble NRA following sonication in the presence of 250 mM KI and repeated osmotic shock. This treatment removed all contaminating soluble NRA from microsomes of uninduced barley roots that had been homogenized in a soluble extract from roots of NO3(-)-induced plants. On continuous sucrose gradients, NRA co-migrated specifically with VO4(-)-sensitive ATPase activity, a plasma membrane (PM) marker; activity of glucose-6-phosphate dehydrogenase, assayed as cytosolic marker, co-migrated with NRA. Microsomal NRA was absent in barley deficient in soluble NR. Perturbation and trypsinolysis experiments with PM vesicles isolated by aqueous two-phase partitioning indicated that NR is associated with the periphery of the cytoplasmic face of the bilayer. These results demonstrate that PM and soluble NRs are essentially the same protein but that the membrane-associated form is tightly bound. Although it is possible that PM-associated NR exists in vivo, unequivocal evidence for this has yet to be shown. However, PM NR is definitely present in vitro.
Document ID
20040090150
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Meyerhoff, P. A.
(University of California Davis 95616, United States)
Fox, T. C.
Travis, R. L.
Huffaker, R. C.
Date Acquired
August 21, 2013
Publication Date
January 1, 1994
Publication Information
Publication: Plant physiology
Volume: 104
ISSN: 0032-0889
Subject Category
Man/System Technology And Life Support
Funding Number(s)
CONTRACT_GRANT: NCC2-99
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Number 61-10
NASA Program CELSS
NASA Discipline Life Support Systems

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