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FabR DNA-binding transcriptional repressor

Synonyms: FabR
FabR, Fatty acid biosynthesis Regulator, represses expression of the fabA and fabB genes, which are essential for the synthesis of monounsaturated fatty acids [3, 4] FabR directly influences membrane lipid homeostasis [3, 4, 5] It is a unique example of a transcription factor exclusively regulating expression of type II fatty acid synthase enzymes [3]
The FabR consensus sequence has been identified as a palindromic sequence with a length of 18 bp [2, 3] DNA binding and repression require the binding of unsaturated acyl-ACP (acyl-acyl carrier protein) or acyl-CoA. Saturated acyl-ACP or acyl-CoA competes with the unsaturated fatty acids for binding to FabR but does not trigger DNA binding [6] Thus, FabR senses the ratio, rather than the absolute amount, of unsaturated and saturated fatty acids and adjusts expression of fabA and fabB to balance the composition of saturated and unsaturated acyl-ACP [6]
The binding site for FabR overlaps with the binding site for FadR, the transcriptional activator for fabA and fabB in the promoter regions of both fabA and fabB.
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Transcription factor      
TF conformation(s):
Name Conformation Type TF-Effector Interaction Type Apo/Holo Conformation Evidence (Confirmed, Strong, Weak) References
FabR     nd nd
Evolutionary Family: TetR/AcrR
Connectivity class: Local Regulator
Gene name: fabR
  Genome position: 4161067-4161771
  Length: 705 bp / 234 aa
Operon name: fabR-yijD
TU(s) encoding the TF:
Transcription unit        Promoter

Regulated gene(s) fabA, fabB
Multifun term(s) of regulated gene(s)
fatty acids and phosphatidic acid (2)
Regulated operon(s) fabA, fabB
First gene in the operon(s) fabA, fabB
Simple and complex regulons FabR,FadR
Simple and complex regulatory phrases Regulatory phrase (List of promoters regulated by the phrase)

Transcription factor binding sites (TFBSs) arrangements       

  Functional conformation Function Promoter Sigma factor Central Rel-Pos Distance to first Gene Genes Sequence LeftPos RightPos Evidence (Confirmed, Strong, Weak) References
  FabR repressor fabAp Sigma70 -19.5 -47.5 fabA
1016509 1016526 [AIBSCS], [BCE], [BPP], [GEA], [HIBSCS] [1], [2], [3]
  FabR repressor fabBp Sigma70 -20.5 -56.5 fabB
2441653 2441670 [BCE], [BPP], [GEA], [HIBSCS] [1], [2], [3]

Evolutionary conservation of regulatory elements    
     Note: Evolutionary conservation of regulatory interactions and promoters is limited to gammaproteobacteria.
Promoter-target gene evolutionary conservation


 [AIBSCS] Automated inference based on similarity to consensus sequences

 [BCE] Binding of cellular extracts

 [BPP] Binding of purified proteins

 [GEA] Gene expression analysis

 [HIBSCS] Human inference based on similarity to consensus sequences


 [1] Feng Y., Cronan JE., 2011, Complex binding of the FabR repressor of bacterial unsaturated fatty acid biosynthesis to its cognate promoters., Mol Microbiol. 80(1):195-218

 [2] McCue L., Thompson W., Carmack C., Ryan MP., Liu JS., Derbyshire V., Lawrence CE., 2001, Phylogenetic footprinting of transcription factor binding sites in proteobacterial genomes., Nucleic Acids Res. 29(3):774-82

 [3] Zhang YM., Marrakchi H., Rock CO., 2002, The FabR (YijC) transcription factor regulates unsaturated fatty acid biosynthesis in Escherichia coli., J Biol Chem. 277(18):15558-65

 [4] Marrakchi H., Zhang YM., Rock CO., 2002, Mechanistic diversity and regulation of Type II fatty acid synthesis., Biochem Soc Trans. 30(Pt 6):1050-5

 [5] Cronan JE., Gelmann EP., 1975, Physical properties of membrane lipids: biological relevance and regulation., Bacteriol Rev. 39(3):232-56

 [6] Zhu K., Zhang YM., Rock CO., 2009, Transcriptional regulation of membrane lipid homeostasis in Escherichia coli., J Biol Chem. 284(50):34880-8

 [7] Ramos JL., Martinez-Bueno M., Molina-Henares AJ., Teran W., Watanabe K., Zhang X., Gallegos MT., Brennan R., Tobes R., 2005, The TetR family of transcriptional repressors., Microbiol Mol Biol Rev. 69(2):326-56

 [8] Bateman A., Birney E., Durbin R., Eddy SR., Howe KL., Sonnhammer EL., 2000, The Pfam protein families database., Nucleic Acids Res. 28(1):263-6

 [9] Perez-Rueda E., Collado-Vides J., 2000, The repertoire of DNA-binding transcriptional regulators in Escherichia coli K-12., Nucleic Acids Res. 28(8):1838-47

 [10] Zhang YM., Rock CO., 2009, Transcriptional regulation in bacterial membrane lipid synthesis., J Lipid Res. 50 Suppl:S115-9

 [11] Fujita Y., Matsuoka H., Hirooka K., 2007, Regulation of fatty acid metabolism in bacteria., Mol Microbiol. 66(4):829-39