The role of glutamine synthetase and glutamine metabolism in nitrogen metabolite repression, a regulatory phenomenon in the lower eukaryote Neurospora crassa

Dunn-Coleman, Nigel; Garrett, Reginald H.

doi:10.1007/bf00268442

Cited by 49 publications

(39 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…gdhA mutants are partially derepressed on ammonium, suggesting that ammonium must be metabolized, possibly to glutamine, to generate the signal(s) for full nitrogen metabolite repression (4,21,22). Previous studies of glnA mutants in A. nidulans and gln-1 mutants in Neurospora crassa have presented conflicting evidence about the role of glutamine and have even led to the suggestion that the glutamine synthetase protein itself may have a regulatory role (10,15,16,17,28,37,38). To further investigate the role of this enzyme in the generation of the signal for nitrogen metabolite repression, we have isolated and characterized the A. nidulans glnA gene.…”

mentioning

confidence: 99%

Role of Glutamine Synthetase in Nitrogen Metabolite Repression in Aspergillus nidulans

et al. 2001

View full text Add to dashboard Cite

Glutamine synthetase (GS), EC 6.3.1.2, is a central enzyme in the assimilation of nitrogen and the biosynthesis of glutamine. We have isolated the Aspergillus nidulans glnA gene encoding GS and have shown that glnA encodes a highly expressed but not highly regulated mRNA. Inactivation of glnA results in an absolute glutamine requirement, indicating that GS is responsible for the synthesis of this essential amino acid. Even when supplemented with high levels of glutamine, strains lacking a functional glnA gene have an inhibited morphology, and a wide range of compounds have been shown to interfere with repair of the glutamine auxotrophy. Heterologous expression of the prokaryotic Anabaena glnA gene from the A. nidulans alcA promoter allowed full complementation of the A. nidulans glnA⌬ mutation. However, the A. nidulans fluG gene, which encodes a protein with similarity to prokaryotic GS, did not replace A. nidulans glnA function when similarly expressed. Our studies with the glnA⌬ mutant confirm that glutamine, and not GS, is the key effector of nitrogen metabolite repression. Additionally, ammonium and its immediate product glutamate may also act directly to signal nitrogen sufficiency.

show abstract

mentioning

confidence: 99%

Role of Glutamine Synthetase in Nitrogen Metabolite Repression in Aspergillus nidulans

et al. 2001

View full text Add to dashboard Cite

show abstract

“…In Neurospora crassa, the expression of many enzymes of nitrogen metabolism is regulated via a nitrogen-specific regulatory circuit (4,10,13). A major regulatory gene, designated nit-2, is responsible for turning on the expression of the various nitrogen-related enzymes and appears to mediate nitrogen catabolite repression, which blocks the expression of many enzymes involved in the use of secondary nitrogen sources when the primary nitrogen source ammonium, glutamine, or glutamate is available.…”

mentioning

confidence: 99%

Induction and de novo synthesis of uricase, a nitrogen-regulated enzyme in Neurospora crassa

Nahm¹,

Marzluf²

1987

J Bacteriol

View full text Add to dashboard Cite

Two efficient procedures are presented for the purification of the purine catabolic enzyme uricase from Neurospora crassa. A specific antiserum for uricase was prepared and used to examine the regulation of uricase expression. Even when wild-type cells are growing under full nitrogen repression conditions, they possess a considerable basal level of uricase. Induction results in a severalfold increase in the level of this enzyme and reflects de novo enzyme synthesis. Identical forms of uricase were translated in vitro from RNA isolated from control and induced cells, but, unexpectedly, induced cells contained less translatable uricase mRNA than did control cells. Although uricase is localized in peroxisomes, the enzyme subunit appears to be synthesized in mature form without any requirement for processing.

show abstract

“…This effect would have to be seen in log-phase cultures grown on ammonium nitrate (results presented here) but not in stationary-phase mycelia cultured with ammonium tartrate and hypoxanthine' (14), possibly due to the existence of a higher arginine pool in stationary-phase mycelia than in rapidly dividing log-phase cultures. However, because the Mr 41,700 species is present at the same levels in strain LA116 as in strain LA1, its regulation must be more sensitive to arginine than that of the 36,100-Mr species or influenced by a secondary metabolite or locus.…”

Section: Methodsmentioning

confidence: 50%

“…Gel slices were diluted in lx Laemmli stacking gel buffer containing 0, 50, or 250 (or 200) ng of Staphylococcus aureus V8 protease. Molecular weight standards were 500 ng each of egg albumin (45,000), glyceraldehyde-3-phosphate dehydrogenase (36,000), ,Blactoglobulin (18,400), and ot-lactalbumin (14,200). Before samples were loaded on the gel, 10 ,u of a solution containing 0.05% bromphenol blue and 80% glycerol was added to all protease and molecular weight standard samples.…”

Section: Methodsmentioning

confidence: 99%

“…The nit-2 gene product is a positive, trans-acting, pleiotropic regulatory effector necessary for expression of genes whose products are required for utilization of several alternative nitrogen sources (31). Glutamine appears to cause inactivation of the nit-2 gene function, possibly through maintenance of an octameric glutamine synthetase, which may itself be the negative effector (14). Arginase levels are unaffected by the nit-2 mutation (15), indicating that the nit-2 regulatory mechanism is not responsible for nitrogen control of arginase levels.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Relationship between two major immunoreactive forms of arginase in Neurospora crassa

Borkovich

Weiss

1987

J Bacteriol

View full text Add to dashboard Cite

Two major immunoreactive proteins of Mr 41,7Q0 and 36,100 have been detected in crude mycelial extracts with polyclonal antibodies raised against arginase purified from Neurospora crassa. The latter corresponded to the protein used to obtain the antibodies. Both polypeptides were either missing or present in very low amounts in mutant strains having little or no detectable arginase activity. The relative proportion of the two species was altered in strains containing the nitrogen catabolite regulatory mutation nit-2. Peptide mapping indicated that the two species are very closely related, but several of the peptides which appeared to be identical by staining reacted differently with the antibodies. Both species were produced by in vitro translation of poly(A)t mRNA, although the larger species was produced to a much smaller extent, than was expected from its abundance in vivo. The results suggest the existence of multiple forms of arginase in N. crassa which differ in their response to nitrogen catabolite regulation.Arginase (EC 3.5.3.1) from Neurospora crassa is a catabolic enzyme which is maximally active under conditions of nitrogen starvation (24) or arginine excess (40). The specific activity of arginase increases threefold when mycelia are grown with arginine as the sole nitrogen source. This induction is accompanied by a 75-fold increase in the cytoplasmic pool of arginine (13). However, it is not known whether this increase jn enzyme activity results from de novo protein synthesis or from activation of preexisting arginase molecules.When a wild-type strain is grown in medium containing glutamine, glutamate, oF ammonium, the addition of arginine causes only a small increase in arginase specific activity (37). This effect has been termed "nitrogen catabolite control." Arginase is present at fully induced levels in mutant strains having the am mutation (lacking NADP:glutamate dehydrogenase, and hence having low glutamate and glutamine pools) whether the strain is grown in arginine alone or in arginine-ammonium medium (37). This suggests that nitrogen catabolite control is mediated by glutamine or glutamate or by a secondary effect directly influenced by these two species.One known nitrogen catabolite repression mechanism is mediated by the nit-2 loc'us in N. crassa. The nit-2 gene product is a positive, trans-acting, pleiotropic regulatory effector necessary for expression of genes whose products are required for utilization of several alternative nitrogen sources (31). Glutamine appears to cause inactivation of the nit-2 gene function, possibly through maintenance of an octameric glutamine synthetase, which may itself be the negative effector (14). Arginase levels are unaffected by the nit-2 mutation (15), indicating that the nit-2 regulatory mechanism is not responsible for nitrogen control of arginase levels. The nmr locus, which is responsible for nitrogen catabolite repression of nitrate assimilatory genes, also does not appear to regulate arginase levels in N. crassa (15, 36).We recently reported prel...

show abstract

The role of glutamine synthetase and glutamine metabolism in nitrogen metabolite repression, a regulatory phenomenon in the lower eukaryote Neurospora crassa

Cited by 49 publications

References 25 publications

Role of Glutamine Synthetase in Nitrogen Metabolite Repression in Aspergillus nidulans

Role of Glutamine Synthetase in Nitrogen Metabolite Repression in Aspergillus nidulans

Induction and de novo synthesis of uricase, a nitrogen-regulated enzyme in Neurospora crassa

Relationship between two major immunoreactive forms of arginase in Neurospora crassa

Contact Info

Product

Resources

About