A feedback-resistant mutant of Bacillus subtilis glutamine synthetase with pleiotropic defects in nitrogen-regulated gene expression.
The Bacillus subtilis TnrA transcription factor regulates gene expression during nitrogen-limited growth. When cells are grown with excess nitrogen, feedback-inhibited glutamine synthetase forms a protein-protein complex with TnrA and prevents TnrA from binding to DNA. A mutation in glutamine synthetase with a phenylalanine replacement at the Ser-186 residue (S186F) was isolated by screening for B. subtilis mutants with constitutive TnrA activity. Although S186F glutamine synthetase has kinetic properties that are similar to the wild-type protein, the S186F enzyme is resistant to feedback inhibition by glutamine and AMP. Ligand binding experiments revealed that the S186F protein had a lower affinity for glutamine and AMP than the wild-type enzyme. S186F glutamine synthetase was defective in its ability to block DNA binding by TnrA in vitro. The properties of the feedback-resistant S186F mutant support the model in which the feedback-inhibited form of glutamine synthetase regulates TnrA activity in vivo.
Wray
Lewis V
LV
Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts 02118-2526, USA.
Fisher
Susan H
SH
D000249:Adenosine Monophosphate / Q000378:metabolism; D019943:Amino Acid Substitution; D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics*; D001665:Binding Sites; D005246:Feedback; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D005973:Glutamine / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D009584:Nitrogen / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D011485:Protein Binding; D014157:Transcription Factors / Q000502:physiology; D001616:beta-Galactosidase / Q000378:metabolism
D008024:Ligands; D014157:Transcription Factors; D005973:Glutamine; D000249:Adenosine Monophosphate; D010649:Phenylalanine; D001616:beta-Galactosidase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen