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The lac operon of Escherichia coli is repressed several 100-fold in the presence of glucose. This repression has been attributed to cAMP receptor protein-mediated inhibition of lac transcription and EIIA Glc -mediated inhibition of lactose transport (inducer exclusion). The growing evidence against the first mechanism has led to the postulate that the repression is driven by inducer exclusion. Although inducer exclusion reduces the permease activity only 2-fold in fully induced cells, it could be more potent in partially induced cells. Here, we show that even in partially induced cells, inducer exclusion reduces the permease activity no more than 6-fold. Moreover, the repression is so small because these experiments are performed in the presence of chloramphenicol. Indeed, when glucose is added to a culture growing on glycerol and TMG, but no chloramphenicol, lac expression is repressed 900-fold. This repression is primarily due to reversal of the positive feedback loop, i.e., the decline of the intracellular TMG level leads to a lower permease level, which reduces the intracellular TMG level even further. The repression in the absence of chloramphenicol is therefore primarily due to positive feedback, which does not exist during measurements of inducer exclusion.

Titel:	Inducer exclusion, by itself, cannot account for the glucose-mediated lac repression of Escherichia coli.
Autor/in / Beteiligte Person:	Aggarwal, RK ; Narang, A
Link:	Zum Volltext
Zeitschrift:	Biophysical journal, Jg. 121 (2022-03-01), Heft 5, S. 820
Veröffentlichung:	Cambridge, MA : Cell Press ; <i>Original Publication</i>: New York, Published by Rockefeller University Press [etc.] for the Biophysical Society., 2022
Medientyp:	academicJournal
ISSN:	1542-0086 (electronic)
DOI:	10.1016/j.bpj.2022.01.016
Schlagwort:	Chloramphenicol metabolism Chloramphenicol pharmacology Glucose metabolism Glucose pharmacology Lac Operon Membrane Transport Proteins genetics Membrane Transport Proteins metabolism Escherichia coli metabolism Lactose metabolism
Sonstiges:	Nachgewiesen in: MEDLINE Sprachen: English Publication Type: Journal Article; Research Support, Non-U.S. Gov't Language: English [Biophys J] 2022 Mar 01; Vol. 121 (5), pp. 820-829. <i>Date of Electronic Publication: </i>2022 Jan 20. MeSH Terms: Escherichia coli* / metabolism ; Lactose* / metabolism ; Chloramphenicol / metabolism ; Chloramphenicol / pharmacology ; Glucose / metabolism ; Glucose / pharmacology ; Lac Operon ; Membrane Transport Proteins / genetics ; Membrane Transport Proteins / metabolism References: Biophys J. 2022 Mar 1;121(5):808-819. (PMID: 35065914) ; J Bacteriol. 1978 Dec;136(3):947-54. (PMID: 214424) ; Nat Rev Microbiol. 2008 Aug;6(8):613-24. (PMID: 18628769) ; Ann N Y Acad Sci. 1963 Jan 21;102:602-20. (PMID: 14034000) ; J Bacteriol. 1982 May;150(2):604-15. (PMID: 6279563) ; FEBS Lett. 1968 Nov;2(1):57-60. (PMID: 11946268) ; Proc Natl Acad Sci U S A. 2007 Apr 3;104(14):6043-8. (PMID: 17376875) ; Genes Cells. 1996 Mar;1(3):293-301. (PMID: 9133663) ; J Biotechnol. 2012 Jan;157(1):82-8. (PMID: 22079752) ; J Theor Biol. 2007 Jan 21;244(2):326-48. (PMID: 16989865) ; Microbiol Mol Biol Rev. 2006 Dec;70(4):939-1031. (PMID: 17158705) ; EMBO J. 1983;2(5):715-20. (PMID: 16453452) ; Biochim Biophys Acta. 1976 Dec 14;457(3-4):213-57. (PMID: 187249) ; J Bacteriol. 1959 Nov;78:624-35. (PMID: 13811044) ; Biochim Biophys Acta. 1959 Feb;31(2):525-38. (PMID: 13628682) ; Proc Natl Acad Sci U S A. 1957 Jul 15;43(7):553-66. (PMID: 16590055) ; Proc Natl Acad Sci U S A. 2015 Feb 24;112(8):2407-12. (PMID: 25675534) ; J Theor Biol. 1972 Jan;34(1):185-92. (PMID: 5017022) ; Nat Rev Microbiol. 2008 Dec;6(12):954; author reply 954. (PMID: 18955986) ; J Biol Chem. 1975 Sep 10;250(17):7078-80. (PMID: 169265) ; Proc Natl Acad Sci U S A. 1975 Jun;72(6):2300-4. (PMID: 166384) ; Anal Biochem. 1973 Jan;51(1):173-9. (PMID: 4688012) ; Nature. 2004 Feb 19;427(6976):737-40. (PMID: 14973486) ; Mol Microbiol. 1998 May;28(4):755-65. (PMID: 9643543) ; J Biol Chem. 1966 May 25;241(10):2200-11. (PMID: 5330114) ; J Biol Chem. 1968 Oct 25;243(20):5420-7. (PMID: 4302785) ; Biochem Biophys Res Commun. 1974 Mar 25;57(2):348-52. (PMID: 4364236) ; J Biol Chem. 1982 Dec 10;257(23):14553-64. (PMID: 6815195) ; Nat Rev Microbiol. 2009 Mar;7(3):250. (PMID: 19230236) ; Bull Math Biol. 2008 May;70(4):1032-64. (PMID: 18246403) ; J Supramol Struct. 1977;6(4):495-502. (PMID: 338995) ; Bull Math Biol. 2009 Feb;71(2):453-514. (PMID: 19067083) ; J Bacteriol. 1959 Nov;78:601-12. (PMID: 13811043) ; Proc Natl Acad Sci U S A. 1997 Nov 25;94(24):12914-9. (PMID: 9371775) ; Biochim Biophys Acta. 1955 Jan;16(1):99-116. (PMID: 14363236) Substance Nomenclature: 0 (Membrane Transport Proteins) ; 66974FR9Q1 (Chloramphenicol) ; IY9XDZ35W2 (Glucose) ; J2B2A4N98G (Lactose) Entry Date(s): Date Created: 20220123 Date Completed: 20220414 Latest Revision: 20230612 Update Code: 20231215 PubMed Central ID: PMC8943701

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Inducer exclusion, by itself, cannot account for the glucose-mediated lac repression of Escherichia coli.