Repression: The Trp and Lac Systems
Repression is an important aspect of the regulation of gene expression in bacteria that is achieved by the interaction of a protein (repressor) with a specific DNA sequence (the operator) in the promoter region of a polycistronic gene. The affinity of the repressor for its operator is modulated by a metabolite that is part of the pathway controlled by the gene products and is thus an example of metabolic or nutrient sensing that is intimately tied to cell metabolism and growth. Repression can be either positive or negative as exemplified by the lac repressor system (positive control) and the trp repressor system (negative control) (Fig. 1).
Cartoon of the operons of lac (negative) and trp (positive) control. p,o represents the promoter and operator sequences, respectively. The promoter is accessed by RNA polymerase only if the operator is not occupied by a repressor molecule. (a) Lac I is the gene for the lac repressor, which is transcribed...
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References
Daber R, Sochor MA, Lewis M (2011) Thermodynamic analysis of mutant lac repressors. J Mol Biol 409:76–87
Fersht A (1999) Structure and mechanism in protein science. W. H. Freeman, New York
Frank DE, Saecker RM, Bond JP, Capp MW, Tsodikov OV, Melcher SE, Levandoski MM, Record MT (1997) Thermodynamics of the interactions of lac repressor with variants of the symmetric lac operator: effects of converting a consensus site to a non-specific site. J Mol Biol 267:1186–1206
Guenot J, Fletterick RJ, Kollman PA (1994) A negative electrostatic determinant mediates the association between the Escherichia coli trp repressor and its operator DNA. Protein Sci 3:1276–1285
Ha JH, Spolar RS, Record MT (1989) Role of the hydrophobic effect in stability of site-specific protein–DNA complexes. J Mol Biol 209:801–816
Joachimiak A, Haran TE, Sigler PB (1994) Mutagenesis supports water mediated recognition in the trp repressor–operator system. EMBO J 13:367–372
Kercher MA, Lu P, Lewis M (1997) Lac repressor–operator complex. Curr Opin Struct Biol 7:76–85
Ladbury JE, Wright JG, Sturtevant JM, Sigler PB (1994) A thermodynamic study of the trp repressor–operator interaction. J Mol Biol 238:669–681
Lane AN, Jenkins TC (2000) Thermodynamics of nucleic acids and their interactions with ligands. Q Rev Biophys 33:255–306
Lin S-Y, Riggs AD (1975) The general affinity of lac repressor for E. coli DNA: implications for gene regulation in procaryotes and eucaryotes. Cell 4:107–111
Mahmutovic A, Berg OG, Elf J (2015) What matters for lac repressor search in vivo – sliding, hopping, intersegment transfer, crowding on DNA or recognition? Nucleic Acids Res 43:3454–3464
Müller-Hill B (1996) The lac operon: a short history of a genetic paradigm. Walter De Gruyter, Berlin
Otwinowski Z, Schevitz RW, Zhang RG, Lawson CL, Joachimiak A, Marmorstein RQ, Luisi BF, Sigler PB (1988) Crystal-structure of trp repressor operator complex at atomic resolution. Nature 335:321–329
Riggs AD, Bourgeois S, Cohn M (1970) The lac repressor–operator interaction. 3. Kinetic studies. J Mol Biol 53:401–417
Romanuka J, Folkers GE, Biris N, Tishchenko E, Wienk H, Bonvin A, Kaptein R, Boelens R (2009) Specificity and affinity of lac repressor for the auxiliary operators O2 and O3 are explained by the structures of their protein–DNA complexes. J Mol Biol 390:478–489
Spolar RS, Record MT (1994) Coupling of local folding to site-specific binding of proteins to DNA. Science 263:777–784
Tempestini A, Monico C, Gardini L, Vanzi F, Pavone FS, Capitanio M (2018) Sliding of a single lac repressor protein along DNA is tuned by DNA sequence and molecular switching. Nucleic Acids Res 46:5001–5011
Yanofsky C (2004) The different roles of tryptophan transfer RNA in regulating trp operon expression in E. coli versus B. subtilis. Trends Genet 20:367–374
Zhang RG, Joachimiak A, Lawson CL, Schevitz RW, Otwinowski Z, Sigler PB (1987) The crystal-structure of trp aporepressor at 1.8-A shows how binding tryptophan enhances DNA affinity. Nature 327:591–597
Zhang H, Zhao DQ, Revington M, Lee WT, Jia X, Arrowsmith C, Jardetzky O (1994) The solution structures of the trp repressor–operator DNA complex. J Mol Biol 238:592–614
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Lane, A.N. (2020). Bacterial Repression, Lac and Trp Systems. In: Roberts, G., Watts, A. (eds) Encyclopedia of Biophysics. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-35943-9_441-1
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DOI: https://doi.org/10.1007/978-3-642-35943-9_441-1
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