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Pathway Description
Operon: Carnitine Operon
Escherichia coli
Category:
Metabolite Pathway
Sub-Category:
Signaling
Created: 2015-09-08
Last Updated: 2025-09-12
The caiTABCDE operon is activated under anaerobic conditions to facilitate the anaerobic metabolism of carnitine. The operon is primarily activated by the ArcA protein, which is phosphorylated by ArcB in response to a reduced quinone pool under low oxygen conditions. This phosphorylated ArcA (ArcA-P) binds upstream of the operon, initiating transcription. Additionally, the CaiF transcriptional activator is induced by the cAMP-CRP complex, which forms when intracellular cAMP levels rise in response to low glucose availability, further enhancing transcription of the operon. The operon encodes proteins like CaiT, a membrane antiporter for L-carnitine, CaiA, CaiB, CaiC, and CaiD, which catalyze various reactions necessary for carnitine metabolism, ensuring efficient energy production under anaerobic conditions.
References
Operon: Carnitine Operon References
Kleber HP: Bacterial carnitine metabolism. FEMS Microbiol Lett. 1997 Feb 1;147(1):1-9.
Pubmed: 9037756
Eichler K, Bourgis F, Buchet A, Kleber HP, Mandrand-Berthelot MA: Molecular characterization of the cai operon necessary for carnitine metabolism in Escherichia coli. Mol Microbiol. 1994 Sep;13(5):775-86.
Pubmed: 7815937
Buchet A, Eichler K, Mandrand-Berthelot MA: Regulation of the carnitine pathway in Escherichia coli: investigation of the cai-fix divergent promoter region. J Bacteriol. 1998 May;180(10):2599-608.
Pubmed: 9573142
Eichler K, Bourgis F, Buchet A, Kleber HP, Mandrand-Berthelot MA: Molecular characterization of the cai operon necessary for carnitine metabolism in Escherichia coli. Mol Microbiol. 1994 Sep;13(5):775-86. doi: 10.1111/j.1365-2958.1994.tb00470.x.
Pubmed: 7815937
Yura T, Mori H, Nagai H, Nagata T, Ishihama A, Fujita N, Isono K, Mizobuchi K, Nakata A: Systematic sequencing of the Escherichia coli genome: analysis of the 0-2.4 min region. Nucleic Acids Res. 1992 Jul 11;20(13):3305-8. doi: 10.1093/nar/20.13.3305.
Pubmed: 1630901
Blattner FR, Plunkett G 3rd, Bloch CA, Perna NT, Burland V, Riley M, Collado-Vides J, Glasner JD, Rode CK, Mayhew GF, Gregor J, Davis NW, Kirkpatrick HA, Goeden MA, Rose DJ, Mau B, Shao Y: The complete genome sequence of Escherichia coli K-12. Science. 1997 Sep 5;277(5331):1453-62. doi: 10.1126/science.277.5331.1453.
Pubmed: 9278503
Eichler K, Schunck WH, Kleber HP, Mandrand-Berthelot MA: Cloning, nucleotide sequence, and expression of the Escherichia coli gene encoding carnitine dehydratase. J Bacteriol. 1994 May;176(10):2970-5. doi: 10.1128/jb.176.10.2970-2975.1994.
Pubmed: 8188598
Drury LS, Buxton RS: DNA sequence analysis of the dye gene of Escherichia coli reveals amino acid homology between the dye and OmpR proteins. J Biol Chem. 1985 Apr 10;260(7):4236-42.
Pubmed: 2984198
Burland V, Plunkett G 3rd, Sofia HJ, Daniels DL, Blattner FR: Analysis of the Escherichia coli genome VI: DNA sequence of the region from 92.8 through 100 minutes. Nucleic Acids Res. 1995 Jun 25;23(12):2105-19. doi: 10.1093/nar/23.12.2105.
Pubmed: 7610040
Iuchi S, Matsuda Z, Fujiwara T, Lin EC: The arcB gene of Escherichia coli encodes a sensor-regulator protein for anaerobic repression of the arc modulon. Mol Microbiol. 1990 May;4(5):715-27. doi: 10.1111/j.1365-2958.1990.tb00642.x.
Pubmed: 2201868
Riley M, Abe T, Arnaud MB, Berlyn MK, Blattner FR, Chaudhuri RR, Glasner JD, Horiuchi T, Keseler IM, Kosuge T, Mori H, Perna NT, Plunkett G 3rd, Rudd KE, Serres MH, Thomas GH, Thomson NR, Wishart D, Wanner BL: Escherichia coli K-12: a cooperatively developed annotation snapshot--2005. Nucleic Acids Res. 2006 Jan 5;34(1):1-9. doi: 10.1093/nar/gkj405. Print 2006.
Pubmed: 16397293
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