An association between photorespiration and protein catabolism: Studies with Chlamydomonas

Cullimore, Julie V.; Sims, A. P.

doi:10.1007/bf00390175

Cited by 105 publications

(36 citation statements)

References 13 publications

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“…The activities of GS were determined by the methods of Cullimore and Sims (17). One unit of GS activity was defined as the amount of enzyme that produced 1 mol of ␥-glutamylhydroxamate per min under the conditions of the assays of GS activities.…”

Section: Construction Of Gs1a-gs1d Chimera and Sitementioning

confidence: 99%

Atomic Structure of Plant Glutamine Synthetase

Unno

Uchida

Sugawara

et al. 2006

Journal of Biological Chemistry

138

195

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Plants provide nourishment for animals and other heterotrophs as the sole primary producer in the food chain. Glutamine synthetase (GS), one of the essential enzymes for plant autotrophy catalyzes the incorporation of ammonia into glutamate to generate glutamine with concomitant hydrolysis of ATP, and plays a crucial role in the assimilation and re-assimilation of ammonia derived from a wide variety of metabolic processes during plant growth and development. Elucidation of the atomic structure of higher plant GS is important to understand its detailed reaction mechanism and to obtain further insight into plant productivity and agronomical utility. Here we report the first crystal structures of maize (Zea mays L.) GS. The structure reveals a unique decameric structure that differs significantly from the bacterial GS structure. Higher plants have several isoenzymes of GS differing in heat stability and catalytic properties for efficient responses to variation in the environment and nutrition. A key residue responsible for the heat stability was found to be Ile-161 in GS1a. The three structures in complex with substrate analogues, including phosphinothricin, a widely used herbicide, lead us to propose a mechanism for the transfer of phosphate from ATP to glutamate and to interpret the inhibitory action of phosphinothricin as a guide for the development of new potential herbicides.Inorganic nitrogen is an essential, often limiting nutrient for plant growth and development. In most natural soils, nitrate is the major form of inorganic nitrogen. After uptake of nitrate, plants first reduce it to ammonia, and then assimilate it into an organic compound as an amide moiety of glutamine. Because glutamine synthetase (GS) 7 catalyzes the very step of assimilation of inorganic nitrogen and because the amide moiety of glutamine is utilized as the donor of amino residue to synthesize a number of essential metabolites such as amino acids, nucleic acids, and amino sugars, glutamine synthesis by plant GS is the cornerstone of plant productivity and thus nitrogen nourishment of all animals on the Earth. For this reason, the importance of plant GS is comparable with that of ribulose-1,5-bisphosphate carboxylase/oxygenase, the carbon dioxide assimilating enzyme (1).Comparison of the primary structures of GSs from prokaryotes and eukaryotes, results in plant GS being categorized as type II, this type commonly occurring in eukaryotes including animals (2). In contrast, type I GS is widely found in prokaryotes (2). The regulatory mechanisms of type I GS activity such as adenylylation and metabolite feedback have been thoroughly characterized (3). The crystal structures of GS from Mycobacterium tuberculosis (4) and Salmonella typhimurium (5) have been determined and the proteins shown to be dodecameric, with each dodecamer being composed of one identical subunit with a molecular mass of about 52 kDa. Types I and II GSs are thought to share a common ancestor but to have diverged into the two types at a very early stage during molecula...

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Section: Construction Of Gs1a-gs1d Chimera and Sitementioning

confidence: 99%

Atomic Structure of Plant Glutamine Synthetase

Unno

Uchida

Sugawara

et al. 2006

Journal of Biological Chemistry

138

195

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“…The transferase activity of Gln synthetase was measured following the procedure of Cullimore and Sims (1980). The assay mixture contained 100 mM Tris-acetate, pH 6.4, 100 mM L-Gln, 60 mM hydroxylamine, 1 mM ADP, 2 mM MnCl 2 , and 40 mM sodium arsenate, an amount of protein extract ranging from 4 to 16 mg (roots) to 18 to 72 mg (leaves) in 1 mL.…”

Section: Gs Protein Analysismentioning

confidence: 99%

Novel Expression Pattern of Cytosolic Gln Synthetase in Nitrogen-Fixing Root Nodules of the Actinorhizal Host, Datisca glomerata

Berry

Murphy²,

Okubara³

et al. 2004

Plant Physiology

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Gln synthetase (GS) is the key enzyme of primary ammonia assimilation in nitrogen-fixing root nodules of legumes and actinorhizal (Frankia-nodulated) plants. In root nodules of Datisca glomerata (Datiscaceae), transcripts hybridizing to a conserved coding region of the abundant nodule isoform, DgGS1-1, are abundant in uninfected nodule cortical tissue, but expression was not detectable in the infected zone or in the nodule meristem. Similarly, the GS holoprotein is immunolocalized exclusively to the uninfected nodule tissue. Phylogenetic analysis of the full-length cDNA of DgGS1-1 indicates affinities with cytosolic GS genes from legumes, the actinorhizal species Alnus glutinosa, and nonnodulating species, Vitis vinifera and Hevea brasilensis. The D. glomerata nodule GS expression pattern is a new variant among reported root nodule symbioses and may reflect an unusual nitrogen transfer pathway from the Frankia nodule microsymbiont to the plant infected tissue, coupled to a distinctive nitrogen cycle in the uninfected cortical tissue. Arg, Gln, and Glu are the major amino acids present in D. glomerata nodules, but Arg was not detected at high levels in leaves or roots. Arg as a major nodule nitrogen storage form is not found in other root nodule types except in the phylogenetically related Coriaria. Catabolism of Arg through the urea cycle could generate free ammonium in the uninfected tissue where GS is expressed.

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“…Determination of enzyme activity Cell-free extracts were assayed for GS transferase (GS,) activity as described by Cullimore & Sims (1980). Molecular mass markers were assayed as described by Cullimore et al…”

Section: High-perjormance Liquid Chromatographymentioning

confidence: 99%

Expression of three plant glutamine synthetase cDNA in Escherichia coli

Bennett

Cullimore

1990

European Journal of Biochemistry

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Three cDNA clones encoding the closely related glutamine synthetase (GS) a, p and y polypeptides of Phaseolus vulgaris (French bean) were recombinantly expressed in Escherichia coli. The GS expression plasmids correctly synthesised the recombinant a, / 3 and y polypeptides which then assembled into catalytically active homo-octameric isoenzymes. These isoenzymes behaved similarly to their native homologues on ion-exchange and gel-filtration chromatography. Furthermore, the M and y isoenzymes complemented a GS(g1nA)-deficient mutant, thus demonstrating their physiological activity in E. coli. Differences were observed between the three recombinant GS plasmids in their quantitative expression of the GS polypeptides and their ability to complement the E. coli mutant. These differences were correlated to the degree of solubility of the polypeptide, which was observed to be dependent on the temperature of expression. The production of active GS isoenzymes in E. coli facilitates the isolation and characterisation of the individual P . vulgaris homo-octameric GS isoenzymes.

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An association between photorespiration and protein catabolism: Studies with Chlamydomonas

Cited by 105 publications

References 13 publications

Atomic Structure of Plant Glutamine Synthetase

Atomic Structure of Plant Glutamine Synthetase

Novel Expression Pattern of Cytosolic Gln Synthetase in Nitrogen-Fixing Root Nodules of the Actinorhizal Host, Datisca glomerata

Expression of three plant glutamine synthetase cDNA in Escherichia coli

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