A b s t r a c t 1 . The optimal conditions for assaying glutamine synthetase activity in tissue homogenates have been investigated. 2. The distribution of the synthetase activity in seventeen species of the vertebrates and one species of Protozoa (Tetrahymena pyriformis) has been studied. 3. The present study shows that a definite correlation exists between the distribution of glutamine synthet...

Yeast glutamine synthetase was purified and shown to be an octameric globular protein (s = 15.4,fF0 = 1-29, mol. wt = 390000). It consists of two weakly-bound half molecules (s = 8.7, fFo = 1-35, mol. wt = 180500) and relatively harsh treatment is required to dissociate these octamers into component monomers (s = 3.8). Deactivation of the enzyme in vivo may include changes in the conformation o...

The regulation of glutamine synthetase (EC 6.3.1.2) from Prochlorococcus was previously shown to exhibit unusual features: it is not upregulated by nitrogen starvation and it is not inactivated by darkness (El Alaoui et al. (2001) Appl Environ Microbiol 67: 2202-2207). These are probably caused by adaptations to oligotrophic environments, as confirmed in this work by the marked decrease in the ...

Free radical-mediated oxidative damage has been implicated in tissue injury resulting from ischemia/reperfusion events. Global cortical ischemia/reperfusion injury to Mongolian gerbil brains was produced by transient occlusion of both common carotid arteries. Protein oxidation, as measured by protein carbonyl content, increased significantly during the reperfusion phase that followed 10 min of ...

Astrocytes are claimed to protect neurons against excitotoxicity by clearing glutamate from the extracellular space and rapidly converting it into glutamine. Glutamine, is then released into the extracellular medium, taken up by neurons and transformed back into glutamate which is then stored into synaptic vesicles. Glutamine synthetase (GS), the key enzyme that governs this glutamate/glutamine...

Tn551 insertional inactivation of femC is known to reduce methicillin resistance levels in methicillin-resistant and -susceptible Staphylococcus aureus. By use of cotransductional crosses, femC was mapped close to thrB on the SmaI-A fragment of the S. aureus NCTC 8325 chromosome. The Tn551 insertion femC::omega 2005 was found to interrupt an open reading frame coding for a putative protein of 1...

Experiments with the soluble supernatant fraction of fetal rat liver indicate that it contains a glutamine-dependent carbamyl phosphate synthetase. This enzyme can utilize ammonia or glutamine as substrate, but the K, for glutamine is low (approximately low5 M) while the Km for ammonium ion-ammonia is at least 100 times higher. The ATP saturation curve for the enzyme appears to be sigmoidal. Th...

The feedback-inhibited form of Bacillus subtilis glutamine synthetase regulates the activity of the TnrA transcription factor through a protein-protein interaction that prevents TnrA from binding to DNA. Five mutants containing feedback-resistant glutamine synthetases (E65G, S66P, M68I, H195Y, and P318S) were isolated by screening for colonies capable of cross-feeding Gln(-) cells. In vitro enz...

A number of glutamine auxotrophs of Salmonella typhimurium were isolated and characterized genetically. Three of the mutations appear to be closely linked and are complemented by episomes carrying the glnA region of Escherichia coli. The lesions in these strains are approximately 20% linked by P1 transduction with a mutation in the rha gene, but are unlinked to ilv. Another mutation causing glu...

The Escherichia coli AmtB protein is member of the ubiquitous Amt family of ammonium transporters. Using a variety of [14C]methylammonium-uptake assays in wild-type E. coli, together with amtB and glutamine synthetase (glnA) mutants, we have shown that the filtration method traditionally used to measure [14C]methylammonium uptake actually measures intracellular accumulation of methylglutamine a...