Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.14 (ATP synthase)
 7,042 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tobacco (Nicotiana tabacum L.) plants were subjected to a prolonged period of sulfur-deprivation to characterize molecular and metabolic mechanisms that permit control of primary N-metabolism under these conditions. Prior to the appearance of chlorotic lesions, sulfur-deprived tobacco leaves showed a strong decrease in the sulfate content and changes in foliar enzyme activities, mRNA accumulation and amino-acid pools. The basic amino acids glutamine, asparagine and arginine accumulated in the leaves of sulfur-deprived plants, while the foliar concentrations of aspartate, glutamate, serine or alanine remained fairly unchanged. Maximal extractable nitrate reductase (NR; EC 1.6.6.1) activity decreased strongly in response to sulfur-deprivation. The decrease in maximal extractable NR activity was accompanied by a decline in NR transcripts while the mRNAs of the plastidic glutamine synthetase (EC 6.1.3.2) or the beta-subunit of the mitochondrial ATP synthase were much less affected. Nitrate first accumulated in leaves of tobacco during sulfur-deprivation but then declined. An appreciable amount of nitrate was, however, present in severely sulfur-depleted leaves. The repression of NR gene expression is, therefore, not related to the decrease in the leaf nitrate level. However, glutamine- and/or asparagine-mediated repression of NR gene transcription is a possible mechanism of control in situations when glutamine and asparagine accumulate in leaves and provides a feasible explanation for the reduction in NR activity during sulfur-deprivation. The removal of reduced nitrogen from primary metabolism by redirection and storage as arginine, asparagine or glutamine combined with the down-regulation of nitrate reduction via glutamine- and/or asparagine-mediated repression of NR gene transcription may contribute to maintaining a normal N/S balance during sulfur-deprivation and indicate that the co-ordination of N- and S-metabolism is retained under these conditions.
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PMID:Negative regulation of nitrate reductase gene expression by glutamine or asparagine accumulating in leaves of sulfur-deprived tobacco. 1103 May 59

The mitochondrial oxidative phosphorylation system in plants possesses a variety of alternative pathways that decrease respiratory ATP production. These alternative pathways are mediated by three classes of bypass proteins: the type II NAD(P)H dehydrogenases (which circumvent complex I of the electron transport chain), the alternative oxidases (AOXs; which circumvent complexes III and IV) and the uncoupling proteins (which circumvent ATP synthase). We have monitored the expression of all genes encoding respiratory bypass proteins in Arabidopsis thaliana growing with different sources of inorganic nitrogen (N). Resupply of nitrate (NO) to N-limited seedling cultures caused a decrease in the transcript abundance of several type II NAD(P)H dehydrogenase and AOX genes, while resupply of ammonium (NH) led to broad increases in expression in the same gene families. Similar results were observed upon switching between nitrate and ammonium in the absence of N stress. Nitrate signalling was found to be mediated primarily by the nitrate ion itself, whereas ammonium regulation was dependent upon assimilation and affected by changes in apoplastic pH. Corresponding alterations in alternative respiratory pathway capacities were apparent in seedlings supplied with either nitrate or ammonium as an N source and in mitochondria purified from the seedlings. Specifically, AOX capacity and protein abundance, as well as calcium-dependent external NADH oxidation, were substantially elevated after growth on ammonium. The increased capacity of respiratory bypass pathways after switching from nitrate to ammonium was correlated to an overall respiratory increase.
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PMID:Reorganization of the alternative pathways of the Arabidopsis respiratory chain by nitrogen supply: opposing effects of ammonium and nitrate. 1646 May 11

Nitrate as one of the two main nitrogen source compounds, acts also as a potent signal substance in plant growth and development. It is increasingly interesting to determine whether nitrate itself or the derived metabolites acts as a signal during the regulation. Rice seedlings were treated with different nitrogen forms (NO(-)(3) vs. NH(+)(4)) and total proteins extracted either from nitrate-fed or ammonium-fed leaves were separated by two-dimensional gel electrophoresis (2-DE), and then the differentially-expressed proteins were identified by MALDI-TOF-MS or ESI-Q-TOF-MS. Twenty-six proteins were up-regulated with NO(-)(3) as the nitrogen source while 6 were up-regulated with NH(+)(4) as the nitrogen source. MS analysis, in combination with database searching, allowed for only a total of 11 proteins identified with significant probability. Among them 7 nitrate-up-regulated proteins were identified, i.e., a PSII oxygen-evolving complex protein 1 (N1), a putative CC-NBS-LRR resistance protein MLA13 (N2), a 23-kD polypeptide of PSII (N3), a translation initiation factor eIF-5A (N5), a putative PSII oxygen-evolving complex protein 2 precursor (N8), an unknown protein (N17), and the ubiquitin carrier protein UBC7 (N18). Four ammonium-up-regulated proteins were identified as the ATP synthase beta subunit (A1), the putative aminotransferase (A3), a hypothetical protein (A5), and OSJNBb0032K15.22 (A6). These results give some new insights into both the biochemical adaptation of plant to different nitrogen forms (NO(-)(3)/NH(+)(4)) and the differences in responses signaled by NO(-)(3)/NH(+)(4) in rice.
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PMID:Differential expression of proteins in rice leaves cultivated with different forms of nitrogen nutrients. 1695 90