Mutations in Bacillus subtilis glutamine synthetase that block its interaction with transcription factor TnrA.
In Bacillus subtilis, the activity of the nitrogen regulatory factor TnrA is regulated through a protein- protein interaction with glutamine synthetase. During growth with excess nitrogen, the feedback-inhibited form of glutamine synthetase binds to TnrA and blocks DNA binding by TnrA. Missense mutations in glutamine synthetase that constitutively express the TnrA-regulated amtB gene were characterized. Four mutant proteins were purified and shown to be defective in their ability to inhibit the in vitro DNA-binding activity of TnrA. Two of the mutant proteins exhibited enzymatic properties similar to those of wild-type glutamine synthetase. A model of B. subtilis glutamine synthetase was derived from a crystal structure of the Salmonella typhimurium enzyme. Using this model, all the mutated amino acid residues were found to be located close to the glutamate entrance of the active site. These results are consistent with the glutamine synthetase protein playing a direct role in regulating TnrA activity.
Department of Microbiology, Boston University School of Medicine, MA 02118, USA. shfisher@bu.edu
Susan H
SH
Fisher
Jaclyn L
JL
Brandenburg
Lewis V
LV
Wray
D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics*; D001426:Bacterial Proteins; D015964:Gene Expression Regulation, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D005973:Glutamine / Q000096:biosynthesis; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D012097:Repressor Proteins; D012486:Salmonella typhimurium / Q000235:genetics; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology
D001426:Bacterial Proteins; D012097:Repressor Proteins; C101458:ScgR protein, Bacillus subtilis; D014157:Transcription Factors; D005973:Glutamine; D005974:Glutamate-Ammonia Ligase