Immunogold localization of glutamine synthetase and NADP-glutamate dehydrogenase of Laccaria laccata in Douglas fir ectomycorrhizas

Mycorrhiza ◽  
1994 ◽  
Vol 5 (2) ◽  
pp. 139-144 ◽  
Author(s):  
A. Brun ◽  
M. Chalot ◽  
R. Duponnois ◽  
B. Botton ◽  
J. Dexheimer
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Douglas Fir ◽  
Laccaria Laccata ◽  
Immunogold Localization

Regulation of glutamine-repressible gene products by the GLN3 function in Saccharomyces cerevisiae

1984 ◽  
Vol 4 (12) ◽  
pp. 2758-2766
Author(s):  
A P Mitchell ◽  
B Magasanik
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Opposite Effect ◽  
Nuclear Gene ◽  
Yeast Saccharomyces Cerevisiae ◽  
Two Dimensional Gel Electrophoresis ◽  
Regulatory Circuit ◽  
Glutamate Dehydrogenase Activity ◽  
Glutamine Limitation

Mutants of the yeast Saccharomyces cerevisiae have been isolated which fail to derepress glutamine synthetase upon glutamine limitation. The mutations define a single nuclear gene, GLN3, which is located on chromosome 5 near HOM3 and HIS1 and is unlinked to the structural gene for glutamine synthetase, GLN1. The three gln3 mutations are recessive, and one is amber suppressible, indicating that the GLN3 product is a positive regulator of glutamine synthetase expression. Four polypeptides, in addition to the glutamine synthetase subunit are synthesized at elevated rates when GLN3+ cultures are shifted from glutamine to glutamate media as determined by pulse-labeling and one- and two-dimensional gel electrophoresis. The response of all four proteins is blocked by gln3 mutations. In addition, the elevated NAD-dependent glutamate dehydrogenase activity normally found in glutamate-grown cells is not found in gln3 mutants. Glutamine limitation of gln1 structural mutants has the opposite effect, causing elevated levels of NAD-dependent glutamate dehydrogenase even in the presence of ammonia. We suggest that there is a regulatory circuit that responds to glutamine availability through the GLN3 product.

Ammonia, glutamine, and asparagine: a carbon–nitrogen interface

1988 ◽  
Vol 66 (10) ◽  
pp. 2103-2109 ◽  
Author(s):  
K. W. Joy
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Higher Plants ◽  
Amino Nitrogen ◽  
Glutamate Synthase ◽  
Dinitrogen Fixation ◽  
Similar Function ◽  
Metabolic Processes ◽  
Organic Form ◽  
Primary Input

In plants, the primary input of nitrogen (obtained from the soil or from symbiotic dinitrogen fixation) occurs through the assimilation of ammonia into organic form. Synthesis of glutamine (via glutamine synthetase) is the major, and possibly exclusive, route for this process, and there is little evidence for the participation of glutamate dehydrogenase. A variety of reactions distribute glutamine nitrogen to other compounds, including transfer to amino nitrogen through glutamate synthase. In many plants asparagine is a major recipient of glutamine nitrogen and provides a mobile reservoir for transport to sites of growth; ureides perform a similar function in some legumes. Utilisation of transport forms of nitrogen, and a number of other metabolic processes, involves release of ammonia, which must be reassimilated. In illuminated leaves, there is an extensive flux of ammonia released by the photorespiratory cycle, requiring continuous efficient reassimilation. Aspects of ammonia recycling and related amide metabolism in higher plants are reviewed.

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