caa a22 4500 477101364 CHVBK 20180405111542.0 cr unu---uuuuu 170330e19960501xx s 000 0 eng 10.1007/BF00196881 doi (NATIONALLICENCE)springer-10.1007/BF00196881 The protein kinase, protein phosphatase and inhibitor protein of nitrate reductase are ubiquitous in higher plants and independent of nitrate reductase expression and turnover [Elektronische Daten] [Johanna Glaab, Werner Kaiser] Nitrate reductase activity and NR protein levels in various leaf tissues were drastically decreased (<3.5% of normal activity) either by keeping detached leaves in continuous darkness for up to 6 d (spinach), or by growing plants (pea, squash) hydroponically on ammonium as the sole N-source, or by germinating and growing etiolated seedlings in complete darkness (squash). The presence of nitrate reductase protein kinase (NRPK), nitrate reductase protein phosphatase (NRPP) and inhibitor protein (IP) was examined by measuring the ability of NR-free desalted extracts to inactivate (ATP-dependent) and reactivate (5′-AMP/EDTA-dependent) added purified spinach NR in vitro. Extracts from low-NR plants (ammonium-grown pea and squash) were also prepared from leaves harvested at the end of a normal light or dark phase, or after treating leaves with anaerobiosis, uncouplers or mannose, conditions which usually activate NR in nitrategrown normal plants. Without exception, extracts from NR-deficient plant tissues were able to inactivate and reactivate purified spinach NR with normal velocity, irrespective of pretreatment or time of harvest. Considerable NRPK, NRPP and IP activities were also found in extracts from almost NR-free ripe fruits (cucumber and tomato). Activities were totally absent, however, in extracts from isolated spinach chloroplasts. The NRPK and IP fractions were partially purified with normal yields from NR-deficient squash or spinach leaves, following the purification protocol worked out for nitrate-grown spinach. The Ca2+/Mg2+-dependent kinase fraction from NR-deficient squash or spinach phosphorylated added purified spinach NR with γ-[32P]ATP and inactivated the enzyme after addition of IP. It is suggested (i) that the auxiliary proteins (NRPK, IP, NRPP) which modulate NR are rather species- or organ-unspecific, (ii) that they do not turn over as rapidly as does NR, (iii) that they are probably expressed independently of NR, and (iiii) that they are not covalently modulated, but under control of metabolic and/or physical signals which are removed by desalting. Springer-Verlag, 1996 Inhibitor protein nationallicence Nitrate reductase nationallicence Protein kinase nationallicence Protein phosphatase nationallicence Protein turnover nationallicence IP : inhibitor protein nationallicence NR : NADH-nitrate reductase nationallicence NRA : nitrate reductase activity nationallicence NRPK : nitrate reductase protein kinase nationallicence NRPP : nitrate reductase protein phosphatase nationallicence PK : protein kinase nationallicence Glaab Johanna Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Mittlerer Dallenbergweg 64, D-97082, Würzburg, Germany aut Kaiser Werner Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Mittlerer Dallenbergweg 64, D-97082, Würzburg, Germany aut Planta Springer-Verlag 199/1(1996-05-01), 57-63 0032-0935 199:1<57 1996 199 425 https://doi.org/10.1007/BF00196881 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00196881 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Glaab Johanna Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Mittlerer Dallenbergweg 64, D-97082, Würzburg, Germany aut NATIONALLICENCE 700 1- Kaiser Werner Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Mittlerer Dallenbergweg 64, D-97082, Würzburg, Germany aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/1(1996-05-01), 57-63 0032-0935 199:1<57 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer