GlnA

• Description: trigger enzyme: glutamine synthetase and effector of TnrA and GlnR
  
  

Gene name	glnA
Synonyms
Essential	no
Product	trigger enzyme: glutamine synthetase
Function	glutamine biosynthesis, control of TnrA and GlnR activity
Gene expression levels in SubtiExpress: glnA
Interactions involving this protein in SubtInteract: GlnA
Metabolic function and regulation of this protein in SubtiPathways: Ammonium/ glutamate
MW, pI	50 kDa, 4.874
Gene length, protein length	1332 bp, 444 aa
Immediate neighbours	glnR, ynxB
Get the DNA and protein sequences (Barbe et al., 2009)
Genetic context This image was kindly provided by SubtiList
Expression at a glance   PubMed

Categories containing this gene/protein

biosynthesis/ acquisition of amino acids, glutamate metabolism, transcription factors and their control, trigger enzyme, phosphoproteins

This gene is a member of the following regulons

GlnR regulon, TnrA regulon

The gene

Basic information

• Locus tag: BSU17460

Phenotypes of a mutant

auxotrophic for glutamine

Database entries

• DBTBS entry: [1]

• SubtiList entry: [2]

The protein

Basic information/ Evolution

• Catalyzed reaction/ biological activity: ATP + L-glutamate + NH₃ = ADP + phosphate + L-glutamine (according to Swiss-Prot)

• Protein family: glutamine synthetase family (according to Swiss-Prot)

• Paralogous protein(s):

Extended information on the protein

• Kinetic information: K(M) for: Glu: 27 mM, ATP: 2.4 mM, ammonium: 0.18 mM; v(max): 3.7 µmol/min/mg

• Domains: glutamate binding flap (aa 300 ... 306: protects unstable intermediates from abberant hydrolysis)

• Modification:
  • phosphorylated on ser/ thr/ tyr PubMed
  • in vitro phosphorylated by PrkC on Thr-26, Thr-147, Ser-207, and Thr-286 PubMed

• Cofactor(s): Mg(2+)

• Effectors of protein activity:
  • feedback inhibition by glutamine, glutamine binds the entrance site for glutamate
  • activity is inhibited upon interaction with TnrA PubMed

• Interactions:
  • TnrA-GlnA PubMed
  • GlnR-GlnA PubMed, (only the feedback-inhibited enzyme interacts with TnrA and GlnR)
  • GlnA-NrgB PubMed

• Localization: cytoplasm (according to Swiss-Prot)

Database entries

• Structure:
  • 3QAJ (complex with ATP)
  • A general discussion of GS structure

• UniProt: P12425

• KEGG entry: [3]

• E.C. number: 6.3.1.2

Additional information

GlnA is a homooligomer of 12 subunits

Expression and regulation

• Operon: glnR-glnA PubMed

• Expression browser: glnA PubMed

• Sigma factor: SigA PubMed

• Regulation:
  • expressed in the absence of glutamine (GlnR) PubMed
  • repressed in the absence of good nitrogen sources (glutamine or ammonium) (TnrA) PubMed

• Regulatory mechanism:
  • GlnR-GlnA complex: transcription repression PubMed
  • TnrA: transcription repression PubMed

• Additional information:

Biological materials

• Mutant: GP247 (cat), available in Stülke lab

• Expression vector:
  • expression/ purification from E. coli, with N-terminal Strep-tag (in pGP172): pGP174, available in Stülke lab

• lacZ fusion: glnR-lacZ: pGP189 (in pAC7), available in Stülke lab

• GFP fusion:

• two-hybrid system:

• Antibody: available in Karl Forchhammer lab

Labs working on this gene/protein

Susan Fisher, Boston, USA homepage