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
Sequences	Protein DNA DNA_with_flanks
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