CitB

• Description: trigger enzyme: aconitase and RNA binding protein
  
  

Gene name	citB
Synonyms
Essential	no
Product	trigger enzyme: aconitate hydratase (aconitase)
Function	TCA cycle
Interactions involving this protein in SubtInteract: CitB
Metabolic function and regulation of this protein in SubtiPathways: Central C-metabolism
MW, pI	99 kDa, 4.903
Gene length, protein length	2727 bp, 909 aa
Immediate neighbours	sspO, yneN
Get the DNA and protein sequences (Barbe et al., 2009)
Genetic context This image was kindly provided by SubtiList

Categories containing this gene/protein

carbon core metabolism, trigger enzyme, RNA binding regulators

This gene is a member of the following regulons

CcpC regulon, CodY regulon, FsrA regulon

The gene

Basic information

• Locus tag: BSU18000

Phenotypes of a mutant

glutamate auxotrophy and a defect in sporulation PubMed

Database entries

• DBTBS entry: [1]

• SubtiList entry: [2]

Additional information

• A mutation was found in this gene after evolution under relaxed selection for sporulation PubMed

The protein

Basic information/ Evolution

• Catalyzed reaction/ biological activity: Citrate = isocitrate (according to Swiss-Prot)
  • Binding to iron responsive elements (IRE RNA) in the absence of the FeS cluster PubMed

• Protein family:

• Paralogous protein(s):

Extended information on the protein

• Kinetic information:

• Domains:

• Modification:

• Cofactor(s): FeS cluster

• Effectors of protein activity:

• Interactions:
  • Mdh-CitB PubMed
  • CitG-CitB PubMed

• Localization:

Database entries

• Structure: 1L5J (E. coli)

• UniProt: P09339

• KEGG entry: [3]

• E.C. number: 4.2.1.3

Additional information

• B. subtilis aconitase is both an enzyme and an RNA binding protein (moonlighting protein) PubMed
• extensive information on the structure and enzymatic properties of CitB can be found at Proteopedia

Expression and regulation

• Operon: citB (according to DBTBS)

• Expression browser: citB PubMed

• Sigma factor: SigA PubMed

• Regulation:
  • repressed during growth in the presence of branched chain amino acids (CodY) PubMed
  • repressed in the presence of glucose and glutamate (CcpC) PubMed
  • expressed upon transition into the stationary phase (AbrB) PubMed, indirect negative regulation by AbrB PubMed
  • repressed by glucose (3.7-fold) (CcpA) PubMed
  • repression by glucose + arginine (CcpC) PubMed
  • less expressed under conditions of extreme iron limitation (FsrA) PubMed
  • part of the iron sparing response (FsrA) PubMed

• Regulatory mechanism:
  • CodY: transcription repression PubMed
  • CcpC: transcription repression (molecular inducer: citrate) PubMed1 PubMed2
  • CcpA: transcription repression PubMed
  • FsrA: translational repression PubMed

• Additional information:

Biological materials

• Mutant: GP683 (erm), available in Stülke lab

• Expression vector:

• lacZ fusion: pGP700 (in pAC5), available in Stülke lab

• GFP fusion:

• two-hybrid system: B. pertussis adenylate cyclase-based bacterial two hybrid system (BACTH), available in Stülke lab

• Antibody: available in Linc Sonenshein lab

Labs working on this gene/protein

Linc Sonenshein, Tufts University, Boston, MA, USA Homepage

Jörg Stülke, University of Göttingen, Germany Homepage

References

Reviews

Karl Volz
The functional duality of iron regulatory protein 1.
Curr Opin Struct Biol: 2008, 18(1);106-11
[PubMed:18261896] [WorldCat.org] [DOI] (P p)

Fabian M Commichau, Jörg Stülke
Trigger enzymes: bifunctional proteins active in metabolism and in controlling gene expression.
Mol Microbiol: 2008, 67(4);692-702
[PubMed:18086213] [WorldCat.org] [DOI] (P p)

Patricia J Kiley, Helmut Beinert
The role of Fe-S proteins in sensing and regulation in bacteria.
Curr Opin Microbiol: 2003, 6(2);181-5
[PubMed:12732309] [WorldCat.org] [DOI] (P p)

R L Switzer
Non-redox roles for iron-sulfur clusters in enzymes.
Biofactors: 1989, 2(2);77-86
[PubMed:2696478] [WorldCat.org] (P p)