CitZ

• Description: citrate synthase
  
  

Gene name	citZ
Synonyms	citA2
Essential	no
Product	citrate synthase II
Function	TCA cycle
Gene expression levels in SubtiExpress: citZ
Interactions involving this protein in SubtInteract: CitZ
Metabolic function and regulation of this protein in SubtiPathways: citZ
MW, pI	41 kDa, 5.451
Gene length, protein length	1116 bp, 372 aa
Immediate neighbours	icd, ytwI
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, phosphoproteins

This gene is a member of the following regulons

CcpA regulon, CcpC regulon

The gene

Basic information

• Locus tag: BSU29140

Phenotypes of a mutant

• glutamate auxotrophy and a defect in sporulation PubMed

Database entries

• BsubCyc: BSU29140

• DBTBS entry: [1]

• SubtiList entry: [2]

The protein

Basic information/ Evolution

• Catalyzed reaction/ biological activity: Acetyl-CoA + H₂O + oxaloacetate = citrate + CoA (according to Swiss-Prot)

• Protein family: citrate synthase family (according to Swiss-Prot)

• Paralogous protein(s): MmgD, CitA

Extended information on the protein

• Kinetic information:
  • Michaelis-Menten (Random Sequential Reaction Mechanism) PubMed
  • specific activity: 0.141 µmol min^-1 (mg protein)^-1 PubMed

• Domains:

• Modification: phosphorylation on Ser-284 PubMed

• Cofactors:

• Effectors of protein activity:
  • Inhibited by acetyl-CoA, 2-oxoglutarate and NADH PubMed FEBS Letters
  • Inhibited by citrate and CoA (competitively against acetyl-CoA and non-competitively against oxaloacetate) PubMed
  • Inhibited by ATP competitively in B. subtilis strain 168 and HS 1A17 PubMed PubMed
    • In B. subtilis strain HS 2A2, ATP inhibits a non-competitive fashion PubMed
  • Activated by AMP PubMed

• Interactions:
  • CitZ-Mdh-Icd (this is the core of the TCA cycle metabolon) PubMed

• Localization:
  • cytoplasm (homogeneously distributed throughout the cell) PubMed

Database entries

• BsubCyc: BSU29140

• Structure:
  • 2C6X
  • A discussion of citrate synthase structure
• UniProt: P39120

• KEGG entry: [3]

• E.C. number: 2.3.3.1

Additional information

• extensive information on the structure and enzymatic properties of CitZ can be found at Proteopedia

Expression and regulation

• Operon:
  • citZ-icd-mdh PubMed

• Expression browser: citZ PubMed

• Sigma factor: SigA PubMed

• Regulation:
  • repression by glucose (6.7-fold) (CcpA) PubMed
  • repression by glucose + glutamate (CcpC) PubMed
  • reduced expression at excess citrate concentrations or iron depletion (CitB) PubMed

• Regulatory mechanism:
  • CcpA: transcription repression, CcpC: transcription repression PubMed
  • CcpC: transcription repression (molecular inducer: citrate) PubMed
  • CitB: mRNA destabilization upon citrate accumulation or iron limitation PubMed

• Additional information:
  • The mRNA has a long 5' leader region. This may indicate RNA-based regulation PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium): 8373 PubMed
  • number of protein molecules per cell (complex medium with amino acids, without glucose): 20578 PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium, exponential phase): 22342 PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium, early stationary phase after glucose exhaustion): 10224 PubMed
  • number of protein molecules per cell (minimal medium with glucose and ammonium, late stationary phase after glucose exhaustion): 18693 PubMed

Biological materials

• Mutant:
  • GP678 (erm), GP797 (spec) available in Jörg Stülke's lab
  • 1A999 ( citZ::spec), PubMed, available at BGSC
  • GP790 (citZ-icd-mdh::kan), available in Jörg Stülke's lab
  • GP797 ( citZ::spec), allows expression of icd and mdh, available in Jörg Stülke's lab

• Expression vector:
  • pGP1120 (N-terminal Strep-tag, for SPINE, purification from B. subtilis, in pGP380) (available in Jörg Stülke's lab)
  • pGP1776 (for expression, purification in E. coli with N-terminal Strep-tag, in pGP172, available in Jörg Stülke's lab)
  • pGP1761 (expression with N-terminal His-tag from E. coli, in pWH844), available in Jörg Stülke's lab

• lacZ fusion:

• GFP fusion:

• 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

Labs working on this gene/protein

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

Jörg Stülke, University of Göttingen, Germany Homepage

References

Reviews

G Wiegand, S J Remington
Citrate synthase: structure, control, and mechanism.
Annu Rev Biophys Biophys Chem: 1986, 15;97-117
[PubMed:3013232] [WorldCat.org] [DOI] (P p)