Faculty Opinions recommendation of Expression of the plastid-located glutamine synthetase of Medicago truncatula. Accumulation of the precursor in root nodules reveals an in vivo control at the level of protein import into plastids.

2003 ◽  
Author(s):  
Jurgen Soll
Keyword(s):  
Glutamine Synthetase ◽  
Medicago Truncatula ◽  
Protein Import ◽  
Root Nodules

scholarly journals Expression of the Plastid-Located Glutamine Synthetase ofMedicago truncatula. Accumulation of the Precursor in Root Nodules Reveals an in Vivo Control at the Level of Protein Import into Plastids

2003 ◽  
Vol 132 (1) ◽  
pp. 390-399 ◽  
Author(s):  
Paula M. Melo ◽  
Lı́gia M. Lima ◽  
Isabel M. Santos ◽  
Helena G. Carvalho ◽  
Julie V. Cullimore
Keyword(s):  
Glutamine Synthetase ◽  
Protein Import ◽  
Root Nodules

Studies on possible routes of ammonium assimilation in soybean root nodule bacteroids

1973 ◽  
Vol 19 (12) ◽  
pp. 1493-1499 ◽  
Author(s):  
Stanley D. Dunn ◽  
Robert V. Klucas
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Reductive Amination ◽  
Root Nodule ◽  
Root Nodules ◽  
Ammonium Assimilation ◽  
Kinetic Properties ◽  
Transferase Activity ◽  
Soybean Root

Glutamine amide–2-oxoglutarate aminotransferase NAD+ oxidoreductase (GOGAT), glutamine synthetase (GS), glutamate dehydrogenase (GD), and alanine dehydrogenase (AD) were studied in soybean root nodules. GS, GOGAT, and AD were present in bacteroids at levels that could account for ammonium assimilation, but GD activity was quite low. The total activities of GS and GD were higher in the cytosol than in the bacteroids by factors of 20 and 7, respectively, whereas GOGAT was not detected in the cytosol. GS (transferase activity) was inhibited by alanine, CTP, glycine, and tryptophan at 5 mM but was relatively unaffected by asparagine, aspartic acid, CMP, glucosamine, and histidine at 5 mM. GOGAT activity was unaffected by ATP, ADP, 8-hydroxyquinoline, and 1,10-phenanthroline but was inhibited by EDTA, citrate, and parachloromercuribenzoate. GOGAT activity (reductive amination) was also inhibited 97% by preincubation with 10−4 M azaserine for 30 min but GD activity was inhibited only 13%. The apparent Km values for NH4+ by AD was 7.4 × 10−3 M and by GD was 7.3 × 10−2 M while for glutamine by GOGAT it was 9.3 × 10−5 M. Activities and kinetic properties for these enzymes may suggest potential routes of nitrogen assimilation in vivo.

scholarly journals Inhibition of Glutamine Synthetase by Phosphinothricin Leads to Transcriptome Reprograming in Root Nodules of Medicago truncatula

2012 ◽  
Vol 25 (7) ◽  
pp. 976-992 ◽  
Author(s):  
Ana R. Seabra ◽  
Patrícia A. Pereira ◽  
Jörg D. Becker ◽  
Helena G. Carvalho
Keyword(s):  
Glutamine Synthetase ◽  
Medicago Truncatula ◽  
Root Nodule ◽  
Higher Plants ◽  
Cell Metabolism ◽  
Root Nodules ◽  
Organic N ◽  
N Availability ◽  
Time Points ◽  
N Assimilation

Glutamine synthetase (GS) is a vital enzyme for the assimilation of ammonia into amino acids in higher plants. In legumes, GS plays a crucial role in the assimilation of the ammonium released by nitrogen-fixing bacteria in root nodules, constituting an important metabolic knob controlling the nitrogen (N) assimilatory pathways. To identify new regulators of nodule metabolism, we profiled the transcriptome of Medicago truncatula nodules impaired in N assimilation by specifically inhibiting GS activity using phosphinothricin (PPT). Global transcript expression of nodules collected before and after PPT addition (4, 8, and 24 h) was assessed using Affymetrix M. truncatula GeneChip arrays. Hundreds of genes were regulated at the three time points, illustrating the dramatic alterations in cell metabolism that are imposed on the nodules upon GS inhibition. The data indicate that GS inhibition triggers a fast plant defense response, induces premature nodule senescence, and promotes loss of root nodule identity. Consecutive metabolic changes were identified at the three time points analyzed. The results point to a fast repression of asparagine synthesis and of the glycolytic pathway and to the synthesis of glutamate via reactions alternative to the GS/GOGAT cycle. Several genes potentially involved in the molecular surveillance for internal organic N availability are identified and a number of transporters potentially important for nodule functioning are pinpointed. The data provided by this study contributes to the mapping of regulatory and metabolic networks involved in root nodule functioning and highlight candidate modulators for functional analysis.

scholarly journals Glutamine Synthetase Is a Molecular Target of Nitric Oxide in Root Nodules of Medicago truncatula and Is Regulated by Tyrosine Nitration

2011 ◽  
Vol 157 (3) ◽  
pp. 1505-1517 ◽  
Author(s):  
Paula M. Melo ◽  
Liliana S. Silva ◽  
Isa Ribeiro ◽  
Ana R. Seabra ◽  
Helena G. Carvalho
Keyword(s):  
Nitric Oxide ◽  
Glutamine Synthetase ◽  
Medicago Truncatula ◽  
Root Nodules ◽  
Molecular Target ◽  
Tyrosine Nitration

scholarly journals Protection Elicited by Two Glutamine Auxotrophs of Mycobacterium tuberculosis and In Vivo Growth Phenotypes of the Four Unique Glutamine Synthetase Mutants in a Murine Model

2006 ◽  
Vol 74 (11) ◽  
pp. 6491-6495 ◽  
Author(s):  
Sunhee Lee ◽  
Bo-Young Jeon ◽  
Svetoslav Bardarov ◽  
Mei Chen ◽  
Sheldon L. Morris ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Glutamine Synthetase ◽  
Mycobacterium Bovis ◽  
Murine Model ◽  
Triple Mutant ◽  
Auxotrophic Mutants ◽  
Bcg Vaccination ◽  
In Vivo Growth ◽  
Subcutaneous Immunization

ABSTRACT We generated four individual glutamine synthetase (GS) mutants (ΔglnA1, ΔglnA2, ΔglnA3, and ΔglnA4) and one triple mutant (ΔglnA1EA2) of Mycobacterium tuberculosis to investigate the roles of GS enzymes. Subcutaneous immunization with the ΔglnA1EA2 and ΔglnA1 glutamine auxotrophic mutants conferred protection on C57BL/6 mice against an aerosol challenge with virulent M. tuberculosis, which was comparable to that provided by Mycobacterium bovis BCG vaccination.

scholarly journals FRAP analysis of nucleocytoplasmic dynamics of the vitamin D receptor splice variant VDRB1: preferential targeting to nuclear speckles

2005 ◽  
Vol 388 (2) ◽  
pp. 509-514 ◽  
Author(s):  
Kathryn L. SUNN ◽  
John A. EISMAN ◽  
Edith M. GARDINER ◽  
David A. JANS
Keyword(s):  
Vitamin D ◽  
Vitamin D Receptor ◽  
Nuclear Import ◽  
Protein Import ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Speckles ◽  
Nuclear Targeting ◽  
Nuclear Retention ◽  
First Time

Although the key components of the cellular nuclear transport machinery have largely been characterized through extensive efforts in recent years, in vivo measurements of the kinetics of nuclear protein import/export are patently few. The present study applies the approach of FRAP (fluorescence recovery after photobleaching) to examine the nucleocytoplasmic flux of a novel human VDRB1 (vitamin D receptor B1) isoform in living cells. Through an N-terminal extension containing a consensus nuclear targeting sequence, VDRB1 is capable of localizing in nuclear speckles adjacent to SC-35 (35 kDa splicing component)-containing speckles as well as in the nucleoplasm, dependent on ligand. Investigation of VDRB1 nucleocytoplasmic transport using FRAP indicates for the first time that the VDRB1 has a serum-modulated, active nuclear import mechanism. There is no evidence of an efficient, active export mechanism for VDRB1, probably as a result of nuclear retention. VDRB1 nuclear import in the absence of serum occurred more rapidly and to a greater extent to nuclear speckles compared with import to other nuclear sites. This preferential transport from the cytoplasm to and accumulation within nuclear speckles is consistent with the idea that the latter represent dynamic centres of VDRB1 interaction with other nuclear proteins. The results are consistent with the existence of specialized pathways to target proteins to nuclear subdomains.

Dynamic organization of the mitochondrial protein import machinery

2016 ◽  
Vol 397 (11) ◽  
pp. 1097-1114 ◽  
Author(s):  
Sebastian P. Straub ◽  
Sebastian B. Stiller ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Dynamics ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Dynamic Cooperation

Abstract Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.

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