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Gene Review

c0460  -  LacI protein

Escherichia coli CFT073

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Disease relevance of c0460

  • It ensures very tight control of the derepression of cell death by the combination of the bacteriophage T7 RNA polymerase-lysozyme system and an inducible synthesis of antisense RNA and the Escherichia coli LacI repressor [1].
  • The lactose repressor protein (LacI), the prototype for genetic regulatory proteins, controls expression of lactose metabolic genes by binding to its cognate operator sequences in E. coli DNA [2].
  • The catabolite control protein (CcpA) from Bacillus megaterium is a member of the bacterial repressor protein family GalR/LacI [3].

High impact information on c0460

  • After inactivation of M.Hha I and LacI, Hae II was used to completely cleave the chromosomes specifically at the inserted lacOs [4].
  • The SsrA-mediated tagging and proteolysis of LacI appears to play a role in cellular adaptation to lactose availability by supporting a rapid induction of lac operon expression [5].
  • SsrA-mediated tagging and proteolysis of LacI and its role in the regulation of lac operon [5].
  • Purified MLAc is folded, fully functional, and binds the inducer isopropyl beta-d-thiogalactoside with the same affinity as wild-type LacI [6].
  • This result compares well with a mathematical model of the binding of the regulatory proteins cAMP receptor protein (CRP) and LacI to the lac regulatory region [7].

Chemical compound and disease context of c0460


Biological context of c0460

  • In addition to providing insight into protein structure-function correlations, LacI has been utilized in a wide variety of applications both in prokaryotic gene expression and in eukaryotic gene regulation and studies of mutagenesis [2].
  • Transformation with a high copy-number plasmid containing the lac operator, lac O, effectively induces kan expression by titrating LacI from the operator [10].
  • When either NLS was placed at the 3' end behind a random nine base pair linker, the activity of the LacI protein depended on the sequence of the linker, and in 9 of 10 linkers tested, activity of the protein was adversely affected [11].
  • At a salt concentration of 0.40 M, the Osym plasmid binding data are consistent with a model with two independent and identical binding sites for operator per LacI tetramer, in which the binding to a site on the tetramer is only slightly more favorable than the reference binding interaction [12].
  • The importance of the structural determination of this domain is underscored by the high degree of sequence homology displayed within the effector binding sites among a sub-class of helix-turn-helix proteins, of which LacI and GalR are members [13].

Anatomical context of c0460

  • The majority of the clonal cell lines created by establishment of the lacI-EBV vector show spontaneous LacI- frequencies of less than 10(-5) and are suitable for studies of induced mutation [14].

Associations of c0460 with chemical compounds

  • In addition to defining the role of Lys55 in PurR minor groove binding, these studies provide structural insight into the minor groove binding specificities of other LacI/GalR family members that have either alanine (e.g. LacI, GalR, CcpA) or a basic residue (e.g. RafR, ScrR, RbtR) at the comparable position [15].
  • In the presence of a XylS effector, such as m-methylbenzoate, the LacI protein is synthesized, preventing the expression of the killing function [16].

Other interactions of c0460


Analytical, diagnostic and therapeutic context of c0460

  • Intact chromosomes from the resulting strains were prepared in agarose microbeads and methylated with Hha I (5'-GCGC) methyltransferase (M.Hha I) in the presence of lac repressor (LacI) [4].
  • By using multiple excitation wavelengths and by carefully examining the behavior of the zero-ET peak during titration with LacI, we show that the LacI-9C14 loop exists exclusively in a single closed form exhibiting essentially 100% ET [17].


  1. A new approach for containment of microorganisms: dual control of streptavidin expression by antisense RNA and the T7 transcription system. Szafranski, P., Mello, C.M., Sano, T., Smith, C.L., Kaplan, D.L., Cantor, C.R. Proc. Natl. Acad. Sci. U.S.A. (1997) [Pubmed]
  2. Lactose repressor protein: functional properties and structure. Matthews, K.S., Nichols, J.C. Prog. Nucleic Acid Res. Mol. Biol. (1998) [Pubmed]
  3. Crystallization and preliminary X-ray analyses of catabolite control protein A, free and in complex with its DNA-binding site. Tebbe, J., Orth, P., Küster-Schöck, E.K., Hillen, W., Saenger, W., Hinrichs, W. Acta Crystallogr. D Biol. Crystallogr. (2000) [Pubmed]
  4. Cleaving yeast and Escherichia coli genomes at a single site. Koob, M., Szybalski, W. Science (1990) [Pubmed]
  5. SsrA-mediated tagging and proteolysis of LacI and its role in the regulation of lac operon. Abo, T., Inada, T., Ogawa, K., Aiba, H. EMBO J. (2000) [Pubmed]
  6. The experimental folding landscape of monomeric lactose repressor, a large two-domain protein, involves two kinetic intermediates. Wilson, C.J., Das, P., Clementi, C., Matthews, K.S., Wittung-Stafshede, P. Proc. Natl. Acad. Sci. U.S.A. (2005) [Pubmed]
  7. Detailed map of a cis-regulatory input function. Setty, Y., Mayo, A.E., Surette, M.G., Alon, U. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
  8. The complexity of nitrosoguanidine mutagenesis increases with size: observations of the mutational specificity of N-propyl-N'-nitro-N-nitrosoguanidine. van der Vliet, G.M., Zielenska, M., Anderson, M.W., Glickman, B.W. Carcinogenesis (1989) [Pubmed]
  9. Excision repair reduces doxorubicin-induced genotoxicity. Anderson, R.D., Veigl, M.L., Baxter, J., Sedwick, W.D. Mutat. Res. (1993) [Pubmed]
  10. Repressor titration: a novel system for selection and stable maintenance of recombinant plasmids. Williams, S.G., Cranenburgh, R.M., Weiss, A.M., Wrighton, C.J., Sherratt, D.J., Hanak, J.A. Nucleic Acids Res. (1998) [Pubmed]
  11. Modifications of the E.coli Lac repressor for expression in eukaryotic cells: effects of nuclear signal sequences on protein activity and nuclear accumulation. Fieck, A., Wyborski, D.L., Short, J.M. Nucleic Acids Res. (1992) [Pubmed]
  12. Cooperative and anticooperative effects in binding of the first and second plasmid Osym operators to a LacI tetramer: evidence for contributions of non-operator DNA binding by wrapping and looping. Levandoski, M.M., Tsodikov, O.V., Frank, D.E., Melcher, S.E., Saecker, R.M., Record, M.T. J. Mol. Biol. (1996) [Pubmed]
  13. Crystallization and preliminary X-ray studies on the co-repressor binding domain of the Escherichia coli purine repressor. Schumacher, M.A., Choi, K.Y., Zalkin, H., Brennan, R.G. J. Mol. Biol. (1992) [Pubmed]
  14. Analysis of mutation in human cells by using an Epstein-Barr virus shuttle system. DuBridge, R.B., Tang, P., Hsia, H.C., Leong, P.M., Miller, J.H., Calos, M.P. Mol. Cell. Biol. (1987) [Pubmed]
  15. The role of lysine 55 in determining the specificity of the purine repressor for its operators through minor groove interactions. Glasfeld, A., Koehler, A.N., Schumacher, M.A., Brennan, R.G. J. Mol. Biol. (1999) [Pubmed]
  16. A substrate-dependent biological containment system for Pseudomonas putida based on the Escherichia coli gef gene. Jensen, L.B., Ramos, J.L., Kaneva, Z., Molin, S. Appl. Environ. Microbiol. (1993) [Pubmed]
  17. Single-molecule spectroscopic determination of lac repressor-DNA loop conformation. Morgan, M.A., Okamoto, K., Kahn, J.D., English, D.S. Biophys. J. (2005) [Pubmed]
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