CitB

• Description: trigger enzyme: aconitase and RNA binding protein
  
  

Gene name	citB
Synonyms
Essential	no
Product	trigger enzyme: aconitate hydratase (aconitase)
Function	TCA cycle
Gene expression levels in SubtiExpress: citB
Interactions involving this protein in SubtInteract: CitB
Metabolic function and regulation of this protein in SubtiPathways: citB
MW, pI	99 kDa, 4.903
Gene length, protein length	2727 bp, 909 aa
Immediate neighbours	sspO, yneN
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

carbon core metabolism, trigger enzyme, RNA binding regulators, most abundant proteins

This gene is a member of the following regulons

CcpA regulon, 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

• BsubCyc: BSU18000

• 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
  • 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:

• Cofactors: FeS cluster

• Effectors of protein activity:

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

• Localization:

Database entries

• BsubCyc: BSU18000

• 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:
  • belongs to the 100 most abundant proteins PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium): 5049 PubMed
  • number of protein molecules per cell (complex medium with amino acids, without glucose): 24371 PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium, exponential phase): 5745 PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium, early stationary phase after glucose exhaustion): 3428 PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium, late stationary phase after glucose exhaustion): 5655 PubMed

Biological materials

• Mutant:
  • GP1275 (citB::erm), available in Jörg Stülke's lab
  • GP1441 (spc), available in Jörg Stülke's lab
  • 1A999 ( citB::spec), PubMed, available at BGSC

• Expression vector:
  • GP1439 (citB-Strep (spc)), purification from B. subtilis, for SPINE, available in Jörg Stülke's lab
  • pGP1810 (for expression, purification in E. coli with N-terminal Strep-tag, in pGP172, available in Jörg Stülke's lab

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

• GFP fusion: GP1434 (spc, based on pGP1870), available in Jörg Stülke's lab

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

• Antibody: available in Linc Sonenshein's lab

• FLAG-tag construct:
  • GP1144 (spc, based on pGP1331), available in Jörg Stülke's lab
  • GP1145 (kan), available in Jörg Stülke's 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)